Bug 68190 UndoManager and perform change operation must call #dispose on change to be executed if validation fails
3.0 Dispose isn't called if the change object couldn't be executed (isValid didn't return a fatal error).
org.eclipse.ltk.ui.refactoring/src/org/eclipse/ltk/internal/ui/refactoring/UIPerformChangeOperation.java
private Display fDisplay;
	private IWizardContainer fWizardContainer;
	
	public UIPerformChangeOperation(Display display, Change change, IWizardContainer container) {
		super(change);
		fDisplay= display;
		fWizardContainer= container;