java.lang.IllegalArgumentException: Tried to pass null folder arg
        at org.openide.filesystems.FileUtil.isParentOf(FileUtil.java:1204)
        at org.openide.filesystems.FileUtil.getRelativePath(FileUtil.java:997)
        at org.netbeans.modules.groovy.support.debug.DebugUtils.getClassFilter(DebugUtils.java:73)
        at org.netbeans.modules.groovy.support.debug.GroovyLineBreakpoint.<init>(GroovyLineBreakpoint.java:99)
        at org.netbeans.modules.groovy.support.debug.GroovyLineBreakpoint.create(GroovyLineBreakpoint.java:129)
        at org.netbeans.modules.groovy.support.debug.GroovyToggleBreakpointActionProvider.doAction(GroovyToggleBreakpointActionProvider.java:109)
        at org.netbeans.spi.debugger.ActionsProvider$1.run(ActionsProvider.java:105)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:572)
        at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:997)