Steps to Reproduce

Run an empty ckeditor without attributes in an embedded zul file

Current Result

page fails to load, error stack contains NPE from ExecutionImpl.encodeURL()

Expected Result

Page loads

Debug Information

Ckeditor has a rendered attribute customConfigurationsPath which is passed through an encodeURL call
In embedded mode, the encodeURL method calls Servlets.isUniversalURL, which checks for string length on a null value

Workaround

Put a default value into ckeditor's
Attached lang-addon sets a default blank string instead of a null value

Add lang-addon to project, add config in zk.xml

  <language-config>
	     <addon-uri>/WEB-INF/lang-addon.xml</addon-uri>
	</language-config>