Cannot create a link at the top level

When I try to create a link between an input port and a couple model at the top level, returns a "Unhandled event loop exception" error. Here is the "Exception Stack Trace" from the error details:

java.lang.NullPointerException
at org.eclipse.gmf.runtime.diagram.ui.editpolicies.SemanticEditPolicy.relationshipTargetHasChanged(SemanticEditPolicy.java:103)
at org.eclipse.gmf.runtime.diagram.ui.editpolicies.SemanticEditPolicy.getCommand(SemanticEditPolicy.java:81)
at DEVSModeler.diagram.edit.policies.DEVSBaseItemSemanticEditPolicy.getCommand(DEVSBaseItemSemanticEditPolicy.java:75)
at org.eclipse.gef.editparts.AbstractEditPart.getCommand(AbstractEditPart.java:473)
at org.eclipse.gmf.runtime.diagram.ui.editparts.GraphicalEditPart.access$1(GraphicalEditPart.java:1)
at org.eclipse.gmf.runtime.diagram.ui.editparts.GraphicalEditPart$1.run(GraphicalEditPart.java:482)
at org.eclipse.emf.transaction.impl.TransactionalEditingDomainImpl.runExclusive(TransactionalEditingDomainImpl.java:313)
at org.eclipse.gmf.runtime.diagram.ui.editparts.GraphicalEditPart.getCommand(GraphicalEditPart.java:477)
at org.eclipse.gef.tools.TargetingTool.getCommand(TargetingTool.java:122)
at org.eclipse.gef.tools.ConnectionEndpointTracker.handleDragInProgress(ConnectionEndpointTracker.java:178)
at org.eclipse.gef.tools.AbstractTool.mouseDrag(AbstractTool.java:994)
at org.eclipse.gef.tools.SelectionTool.mouseDrag(SelectionTool.java:511)
at org.eclipse.gef.EditDomain.mouseDrag(EditDomain.java:230)
at org.eclipse.gef.ui.parts.DomainEventDispatcher.dispatchMouseMoved(DomainEventDispatcher.java:357)
at org.eclipse.draw2d.LightweightSystem$EventHandler.mouseMove(LightweightSystem.java:533)
at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:199)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1003)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3910)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3503)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2405)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2369)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2221)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:500)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:493)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:113)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:194)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:368)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:559)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:514)
at org.eclipse.equinox.launcher.Main.run(Main.java:1311)