BlueJ Won't Start about pmd-bluej HOT 1 CLOSED

ExtensionWrapper.safeStartup: Class=net.sourceforge.pmd.PMDExecExt Exception=null
java.lang.NullPointerException
	at bluej.extensions.BlueJ.getCurrentFrame(BlueJ.java:272)
	at net.sourceforge.pmd.PMDExecExt.startup(PMDExecExt.java:20)
	at bluej.extmgr.ExtensionWrapper.safeStartup(ExtensionWrapper.java:545)
	at bluej.extmgr.ExtensionWrapper.newExtension(ExtensionWrapper.java:221)
	at bluej.extmgr.ExtensionsManager.loadDirectoryExtensions(ExtensionsManager.java:169)
	at bluej.extmgr.ExtensionsManager.loadExtensions(ExtensionsManager.java:105)
	at bluej.extmgr.ExtensionsManager.getInstance(ExtensionsManager.java:66)
	at bluej.Main.lambda$new$1(Main.java:127)
	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)