Why do I get a Java Exception when I use 'doc' command (2018b)

When using the 'doc' command with a string that is not a command, e.g.:

doc classes

I get a Java Exception event:

Exception in thread "AWT-EventQueue-0": java.lang.NullPointerException
  at com.mathworks.help.helpui.DocRoot.buildDocPageUrl(DocRoot.java:44)
  at com.mathworks.help.helpui.DocPageUrlBuilder.buildDocPageUrl(DocPageUrlBuilder.java:25)
  at com.mathworks.help.helpui.DocPageUrlBuilder.buildFileUrl(DocPageUrlBuilder.java:21)
  at com.mathworks.mlwidgets.help.LightweightHelpPanel$JsHelpPanelClientRunnable.getUrlToLoad(LightweightHelpPanel.java:224)
  at com.mathworks.mlwidgets.help.LightweightHelpPanel$JsHelpPanelClientRunnable.run(LightweightHelpPanel.java:208)
  at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
  at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
  at java.awt.EventQueue.access$500(EventQueue.java:97)
  at java.awt.EventQueue$3.run(EventQueue.java:709)
  at java.awt.EventQueue$3.run(EventQueue.java:703)
  at java.security.AccessController.doPrivileged(Native Method)
  at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
  at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
  at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
  at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
  at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
  at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
  at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
  at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

It works if I use something that is a command, e.g.:

 doc classdef

I'm on Linux Ubuntu 18.04. It was fine in R2018a.

Answer 1

[Richard Stephens]

This problem has gone away after sorting the associated problem. See:

https://uk.mathworks.com/matlabcentral/answers/423210-why-is-matlab-help-browser-showing-unformatted-text-on-linux-r2018b#answer_346722

Answer 2

[Thomas Andersen]

Are there any solutions to this?