[Solved] AddAssertionPanel (still) not working on macOS (SoapUI 5.4.0, macOS 10.13.3)

Hi fellow testers,

I have trouble working with SoapUI on Mac and I hope that someone is able to help me:

I am not able to add assertions to a SoapUI project (existing/new does not matter). Whenever I open the AddAssertionPanel from a test step, the dialog is shown but I am not able to choose an assertion category from the left hand panel or an assertion from the right hand panel.

Steps to reproduce:

• macOS 10.13.2
• Bundled JRE and Oracle Java 1.8.0_161
• SoapUI 5.4.0 (ZIP or installer)
• create new project
• add WSDL and generate test cases
• open one test step
• open assertion panel
• try to choose an assertion category or an assertion
• nothing happens in the GUI
• in the log an exception is being thrown:

java.lang.NullPointerException
	at com.eviware.soapui.impl.wsdl.panels.assertions.AddAssertionPanel$CategoryListRenderer.getTableCellRendererComponent(AddAssertionPanel.java:472)
	at javax.swing.JTable$AccessibleJTable.getAccessibleAt(JTable.java:6990)
	at sun.lwawt.macosx.CAccessibility$23.call(CAccessibility.java:416)
	at sun.lwawt.macosx.CAccessibility$23.call(CAccessibility.java:395)
	at sun.lwawt.macosx.LWCToolkit$CallableWrapper.run(LWCToolkit.java:597)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:301)
	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.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:90)
	at java.awt.EventQueue$4.run(EventQueue.java:731)
	at java.awt.EventQueue$4.run(EventQueue.java:729)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:109)
	at java.awt.WaitDispatchSupport$2.run(WaitDispatchSupport.java:184)
	at java.awt.WaitDispatchSupport$4.run(WaitDispatchSupport.java:229)
	at java.awt.WaitDispatchSupport$4.run(WaitDispatchSupport.java:227)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.awt.WaitDispatchSupport.enter(WaitDispatchSupport.java:227)
	at java.awt.Dialog.show(Dialog.java:1084)
	at java.awt.Component.show(Component.java:1671)
	at java.awt.Component.setVisible(Component.java:1623)
	at java.awt.Window.setVisible(Window.java:1014)
	at java.awt.Dialog.setVisible(Dialog.java:1005)
	at com.eviware.soapui.impl.wsdl.actions.project.SimpleDialog.setVisible(SimpleDialog.java:126)
	at com.eviware.soapui.impl.wsdl.teststeps.actions.AddAssertionAction$1.run(AddAssertionAction.java:58)
	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)

Addition information:

If you click in the category part of the dialog, it seems, that this part is being highlighted/active, here is a small blue border around it.