The ribbon desapears when I handle tables
How to reproduce it :

• Open a content (I opened a program)
• In a rich text field, insert a table
• Enter some content inside the cells of the table
• select all cells and click on the button "Top left corner" of the table tab, in the align group
• Then I go to the edit tab.
• > an error occurs and the ribbon has disappears. I can get the ribbon again but it is displayed above the workspace

  TypeError: Cannot read property 'contextualTab' of undefined
  TypeError: Cannot read property 'contextualTab' of undefined
  at constructor.showContextualTab (http://berlioz.anyware.corp:8093/cms/plugins/core-ui/resources/js/Ametys/ui/fluent/ribbon/TabPanel.js:479:211)
  at constructor.panel.showContextualTab (http://berlioz.anyware.corp:8093/cms/plugins/core-ui/resources/js/Ametys/ui/fluent/ribbon/TabPanel.js:284:34)
  at http://berlioz.anyware.corp:8093/cms/plugins/core-ui/resources/js/Ametys/ribbon/element/RibbonTabController.js:66:20
  at Array.forEach (<anonymous>)
  at Object.Ext.Array.ExtArray.forEach (http://berlioz.anyware.corp:8093/cms/plugins/extjs6/resources/ext-all-debug.js:3302:23)
  at constructor.show (http://berlioz.anyware.corp:8093/cms/plugins/core-ui/resources/js/Ametys/ribbon/element/RibbonTabController.js:65:17)
  at constructor._onSelectionChanged (http://berlioz.anyware.corp:8093/cms/plugins/core-ui/resources/js/Ametys/ribbon/element/tab/TabController.js:248:11)
  at constructor.fire (http://berlioz.anyware.corp:8093/cms/plugins/core-ui/resources/js/Ametys/message/MessageBus.js:169:36)
  at constructor.cb (http://berlioz.anyware.corp:8093/cms/plugins/core-ui/resources/js/Ametys/message/MessageMethods.js:152:31)
  at http://berlioz.anyware.corp:8093/cms/plugins/extjs6/resources/ext-all-debug.js:7101:35