Exception thrown when creating flow path with graphical editor.

[philip-alldredge]

Summary
When attempting to create a flow path with the graphical editor, an exception is thrown repeatedly and the flow path cannot be created.

Expected behavior
Flow path is created.

Actual behavior
An exception is thrown and it does not allow completing the flow path.

Steps To Reproduce

• If you can provide a small model or test case that demonstrates the issue, it will be much easier to debug.
• Paste small code snippets in the three backticks below, larger ones should be put in a gist

1. Create a diagram using the provided model.
2. Create a diagram with the following structure:
   • flow_test_a
     • top.impl
       • ss1 and all data ports
3. Start creating a flow path from i1 to o1.
4. An exception is thrown repeatedly after selecting i1 and it does not allow creating the flow path. Exception is shown in log.

package flow_test_a
public

	system top
		features
			i1: in data port;
			o1: out data port;
			i2: in data port;
			o2: out data port;
	end top;

	system implementation top.impl
		subcomponents
			ss1: system subsystem;
	end top.impl;

	system subsystem
		features
			i1: in data port;
			o2: out data port;
			i2: in data port;
			o1: out data port;
	end subsystem;
end flow_test_a;

Desktop (please complete the following information):

• OSATE Version: Development version
• Operating System: Windows 10

Additional context
Exception

Exception in thread "JavaFX Application Thread" java.lang.UnsupportedOperationException
	at java.base/java.util.ImmutableCollections.uoe(ImmutableCollections.java:142)
	at java.base/java.util.ImmutableCollections$AbstractImmutableCollection.retainAll(ImmutableCollections.java:153)
	at org.osate.ge.aadl2.ui.internal.palette.CreateFlowPathSpecificationPaletteCommand.getPotentialOwners(CreateFlowPathSpecificationPaletteCommand.java:120)
	at org.osate.ge.aadl2.ui.internal.palette.CreateFlowPathSpecificationPaletteCommand.getOperation(CreateFlowPathSpecificationPaletteCommand.java:72)
	at java.base/java.util.Optional.flatMap(Optional.java:289)
	at org.osate.ge.gef.ui.editor.CreateConnectionInteraction.onMouseMoved(PaletteCommandInputEventHandler.java:278)
	at org.osate.ge.gef.ui.editor.BaseInteraction.handleEvent(BaseInteraction.java:43)
	at org.osate.ge.gef.ui.editor.AgeEditor.lambda$19(AgeEditor.java:957)
	at org.osate.ge.gef.ui.editor.AgeEditor.lambda$20(AgeEditor.java:983)
	at javafx.base/com.sun.javafx.event.CompositeEventHandler$NormalEventFilterRecord.handleCapturingEvent(CompositeEventHandler.java:321)
	at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchCapturingEvent(CompositeEventHandler.java:98)
	at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchCapturingEvent(EventHandlerManager.java:221)
	at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchCapturingEvent(EventHandlerManager.java:180)
	at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchCapturingEvent(CompositeEventDispatcher.java:43)
	at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:52)
	at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
	at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
	at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
	at javafx.graphics/javafx.scene.Scene$MouseHandler.process(Scene.java:3897)
	at javafx.graphics/javafx.scene.Scene.processMouseEvent(Scene.java:1878)
	at javafx.graphics/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2623)
	at javafx.graphics/com.sun.javafx.tk.quantum.EmbeddedScene.lambda$mouseEvent$4(EmbeddedScene.java:289)
	at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
	at javafx.graphics/com.sun.javafx.tk.quantum.EmbeddedScene.lambda$mouseEvent$5(EmbeddedScene.java:282)
	at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:457)
	at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
	at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:456)
	at org.eclipse.swt.internal.win32.OS.DispatchMessage(Native Method)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3630)
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1155)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1046)
	at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:155)
	at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:644)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
	at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:551)
	at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:156)
	at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:152)
	at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:203)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:136)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:401)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:255)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:568)
	at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:659)
	at org.eclipse.equinox.launcher.Main.basicRun(Main.java:596)
	at org.eclipse.equinox.launcher.Main.run(Main.java:1467)
	at org.eclipse.equinox.launcher.Main.main(Main.java:1440)