Unable to export to web.
java.util.ConcurrentModificationException
	at java.base/java.util.LinkedList$ListItr.checkForComodification(LinkedList.java:970)
	at java.base/java.util.LinkedList$ListItr.next(LinkedList.java:892)
	at java.base/java.util.Collections$UnmodifiableCollection$1.next(Collections.java:1045)
	at ptolemy.vergil.basic.export.web.DefaultIconScript._provideAttributes(DefaultIconScript.java:196)
	at ptolemy.vergil.basic.export.web.WebContent.provideContent(WebContent.java:176)
	at ptolemy.vergil.basic.export.html.ExportHTMLAction.writeHTML(ExportHTMLAction.java:745)
	at ptolemy.vergil.basic.BasicGraphFrame.writeHTML(BasicGraphFrame.java:1657)
	at ptolemy.vergil.basic.export.html.ExportHTMLAction$1$1.run(ExportHTMLAction.java:559)
	at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:313)
	at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:770)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
	at java.base/java.security.AccessController.doPrivileged(Native Method)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
	at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:740)
	at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
Jun 06, 2022 2:25:43 AM sun.awt.X11.XToolkit processException
WARNING: Exception on Toolkit thread
java.lang.NullPointerException
	at java.desktop/java.awt.Component$BltBufferStrategy.contentsLost(Component.java:4584)
	at java.desktop/java.awt.Component$BltSubRegionBufferStrategy.showIfNotLost(Component.java:4647)
	at java.desktop/javax.swing.BufferStrategyPaintManager.show(BufferStrategyPaintManager.java:208)
	at java.desktop/javax.swing.RepaintManager.show(RepaintManager.java:1430)
	at java.desktop/javax.swing.SwingPaintEventDispatcher.createPaintEvent(SwingPaintEventDispatcher.java:61)
	at java.desktop/sun.awt.X11.XWindow.postPaintEvent(XWindow.java:568)
	at java.desktop/sun.awt.X11.XContentWindow.postPaintEvent(XContentWindow.java:180)
	at java.desktop/sun.awt.X11.XWindow.handleExposeEvent(XWindow.java:562)
	at java.desktop/sun.awt.X11.XContentWindow.handleExposeEvent(XContentWindow.java:151)
	at java.desktop/sun.awt.X11.XBaseWindow.dispatchEvent(XBaseWindow.java:1132)
	at java.desktop/sun.awt.X11.XBaseWindow.dispatchToWindow(XBaseWindow.java:1108)
	at java.desktop/sun.awt.X11.XToolkit.dispatchEvent(XToolkit.java:621)
	at java.desktop/sun.awt.X11.XToolkit.run(XToolkit.java:736)
	at java.desktop/sun.awt.X11.XToolkit.run(XToolkit.java:652)
	at java.base/java.lang.Thread.run(Thread.java:834)