Bug 277966 [Databinding] regression: ObservablesManager throws NPE on dispose if one of the observables is already disposed
tests/org.eclipse.jface.tests.databinding/src/org/eclipse/core/tests/databinding/ObservablesManagerTest.java
*
		 * @see org.eclipse.core.databinding.observable.IObservable#isStale()
		 */
		public boolean isStale() {
			
			return false;
		}
		/*
		 * (non-Javadoc)
		 *
		 * @see org.eclipse.core.databinding.observable.IObservable#removeChangeListener(org.eclipse.core.databinding.observable.IChangeListener)
		 */
		public void removeChangeListener(IChangeListener listener) {
			
		}
		public void removeDisposeListener(IDisposeListener listener) {
			
			
		}
		/*
		 * (non-Javadoc)
		 *
		 * @see org.eclipse.core.databinding.observable.IObservable#removeStaleListener(org.eclipse.core.databinding.observable.IStaleListener)
		 */
		public void removeStaleListener(IStaleListener listener) {
			
		}
	}
}