Bug 32384 Cannot open type hierarchy after a cancel
JUnit setup 1) open the type hierarchy on TestCase 2) press F4 on Object 3) cancel in progress bar 4) press F4 on Object again ->nothing happens
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/typehierarchy/TypeHierarchyViewPart.java
fHistoryDropDownAction.setEnabled(false);
		
		fToggleOrientationActions= new ToggleOrientationAction[] {
			new ToggleOrientationAction(this, VIEW_ORIENTATION_VERTICAL),
			new ToggleOrientationAction(this, VIEW_ORIENTATION_HORIZONTAL),
			new ToggleOrientationAction(this, VIEW_ORIENTATION_SINGLE)
		};
			
		fEnableMemberFilterAction= new EnableMemberFilterAction(this, false);
		fShowQualifiedTypeNamesAction= new ShowQualifiedTypeNamesAction(this, false);
		
		fFocusOnTypeAction= new FocusOnTypeAction(this);
				
		fPaneLabelProvider= new JavaUILabelProvider();
		
		fAddStubAction= new AddMethodStubAction();
		fFocusOnSelectionAction= new FocusOnSelectionAction(this);	
	
		fPartListener= new IPartListener2() {
			public void partVisible(IWorkbenchPartReference ref) {
				IWorkbenchPart part= ref.getPart(false);
				if (part == TypeHierarchyViewPart.this) {
					visibilityChanged(true);
				}
			}
			public void partHidden(IWorkbenchPartReference ref) {
				IWorkbenchPart part= ref.getPart(false);
				if (part == TypeHierarchyViewPart.this) {
					visibilityChanged(false);
				}