Replace:

return 'plugins/repository/binary/'wsp+path'/'property'?mime-type='+mime;

by:

return contextPath+workspaceURI+'/binary/'wsp+path'/'property'?mime-type='+mime;

And add in index.xsl :

<script type="text/javascript">var contextPath = "<xsl:value-of select="$contextPath"/>";</script>