How to reproduce :

• in [skin]/conf/edition-styles.xml, comment the line of the unordered list icon like this :

  <unorderedlist>
  		<import>
  			<button>css/bo/buttons.css</button>
  			<inline-editor>css/bo/editor-content.css</inline-editor>
  		</import>
  		<style>
  			<button>
  <!-- 				<icon>img/postbullets.png</icon> -->
  				<label i18n="true">SKIN_BO_EDITOR_STYLES_UNORDEREDLIST_CUSTOM</label>
  				<description i18n="true">SKIN_BO_EDITOR_STYLES_UNORDEREDLIST_CUSTOM_DESC</description>
  			</button>
  			<inline-editor>custom</inline-editor>
  		</style>
  	</unorderedlist>

• then restart the CMS
  > this trace appears :

  Date:			Thu Aug 14 15:39:35 CEST 2014 (1408023575535)
  Thread:		http-bio-8105-exec-1
  Message #:	309
  Level:		ERROR
  NDC:			
  Category:	sitemap.handled-errors
  Message:		Failed to process pipeline
  	at <map:serialize type="xml"> - resource://org/ametys/web/workspace/sitemap.xmap:99:44
  	at <map:generate type="workspace"> - resource://org/ametys/web/workspace/sitemap.xmap:96:64
  	at <map:serialize type="xhtml"> - resource://org/ametys/web/workspace/sitemap.xmap:214:47
  	at <map:transform type="i18n"> - resource://org/ametys/web/workspace/sitemap.xmap:211:45
  	at <map:transform type="xslt"> - resource://org/ametys/web/workspace/sitemap.xmap:200:71
  	at <map:transform type="i18n"> - resource://org/ametys/web/workspace/sitemap.xmap:197:45
  	at <map:mount> - resource://org/ametys/runtime/kernel/sitemap.xmap:199:109
  Location:	org.ametys.runtime.util.SLF4JLogger.error(SLF4JLogger.java:64)
  Thrown:
  org.apache.cocoon.ProcessingException: Failed to process pipeline
  	at <map:serialize type="xml"> - resource://org/ametys/web/workspace/sitemap.xmap:99:44
  	at <map:generate type="workspace"> - resource://org/ametys/web/workspace/sitemap.xmap:96:64
  	at <map:serialize type="xhtml"> - resource://org/ametys/web/workspace/sitemap.xmap:214:47
  	at <map:transform type="i18n"> - resource://org/ametys/web/workspace/sitemap.xmap:211:45
  	at <map:transform type="xslt"> - resource://org/ametys/web/workspace/sitemap.xmap:200:71
  	at <map:transform type="i18n"> - resource://org/ametys/web/workspace/sitemap.xmap:197:45
  	at <map:mount> - resource://org/ametys/runtime/kernel/sitemap.xmap:199:109
  	at org.apache.cocoon.ProcessingException.throwLocated(ProcessingException.java:145)
  	at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.handleException(AbstractProcessingPipeline.java:953)
  	at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.processXMLPipeline(AbstractProcessingPipeline.java:583)
  	at org.apache.cocoon.components.pipeline.impl.AbstractCachingProcessingPipeline.processXMLPipeline(AbstractCachingProcessingPipeline.java:280)
  	at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.process(AbstractProcessingPipeline.java:780)
  	at org.apache.cocoon.components.source.impl.SitemapSource.toSAX(SitemapSource.java:414)
  	at org.apache.cocoon.components.source.SourceUtil.toSAX(SourceUtil.java:101)
  	at org.apache.cocoon.components.source.SourceUtil.parse(SourceUtil.java:321)
  	at org.apache.cocoon.sitemap.ContentAggregator.generate(ContentAggregator.java:125)
  	at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.processXMLPipeline(AbstractProcessingPipeline.java:579)
  	at org.apache.cocoon.components.pipeline.impl.AbstractCachingProcessingPipeline.processXMLPipeline(AbstractCachingProcessingPipeline.java:280)
  	at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.process(AbstractProcessingPipeline.java:481)
  	at org.apache.cocoon.components.treeprocessor.sitemap.SerializeNode.invoke(SerializeNode.java:144)
  	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:47)
  	at org.apache.cocoon.components.treeprocessor.sitemap.ActTypeNode.invoke(ActTypeNode.java:139)
  	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:47)
  	at org.apache.cocoon.components.treeprocessor.sitemap.MatchNode.invoke(MatchNode.java:108)
  	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:69)
  	at org.apache.cocoon.components.treeprocessor.sitemap.PipelineNode.invoke(PipelineNode.java:143)
  	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:69)
  	at org.apache.cocoon.components.treeprocessor.sitemap.PipelinesNode.invoke(PipelinesNode.java:93)
  	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:236)
  	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:178)
  	at org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:254)
  	at org.apache.cocoon.components.treeprocessor.sitemap.MountNode.invoke(MountNode.java:118)
  	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:47)
  	at org.apache.cocoon.components.treeprocessor.sitemap.MatchNode.invoke(MatchNode.java:108)
  	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:69)
  	at org.apache.cocoon.components.treeprocessor.sitemap.PipelineNode.invoke(PipelineNode.java:143)
  	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:69)
  	at org.apache.cocoon.components.treeprocessor.sitemap.PipelinesNode.invoke(PipelinesNode.java:93)
  	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:236)
  	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:178)
  	at org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:254)
  	at org.apache.cocoon.Cocoon.process(Cocoon.java:699)
  	at org.apache.cocoon.servlet.CocoonServlet.service(CocoonServlet.java:1159)
  	at org.ametys.runtime.servlet.RuntimeServlet._doService(RuntimeServlet.java:135)
  	at org.ametys.runtime.servlet.RuntimeServlet.service(RuntimeServlet.java:92)
  	at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
  	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
  	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
  	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
  	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
  	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
  	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)
  	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
  	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:405)
  	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:964)
  	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:515)
  	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302)
  	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
  	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
  	at java.lang.Thread.run(Unknown Source)
  Caused by: java.lang.NullPointerException
  	at org.ametys.runtime.util.I18nizableText.toSAX(I18nizableText.java:254)
  	at org.ametys.runtime.ui.SAXClientSideElementHelper.saxDefinition(SAXClientSideElementHelper.java:84)
  	at org.ametys.cms.workspace.ribbon.RibbonConfigurationManager.saxRibbonDefinition(RibbonConfigurationManager.java:354)
  	at org.ametys.cms.workspace.WorkspaceGenerator.doGenerate(WorkspaceGenerator.java:117)
  	at org.ametys.web.workspace.WorkspaceGenerator.generate(WorkspaceGenerator.java:91)
  	at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.processXMLPipeline(AbstractProcessingPipeline.java:579)
  	... 52 more