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
private DataBindingContext dbc;
	/*
	 * (non-Javadoc)
	 *
	 * @see org.eclipse.jface.tests.databinding.AbstractDefaultRealmTestCase#setUp()
	 */
	protected void setUp() throws Exception {
		super.setUp();
		dbc = new DataBindingContext();
	}
	/*
	 * (non-Javadoc)
	 *
	 * @see org.eclipse.jface.tests.databinding.AbstractDefaultRealmTestCase#tearDown()
	 */
	protected void tearDown() throws Exception {
		if (dbc != null) {
			dbc.dispose();
		}
		super.tearDown();
	}
	public void testOnlyModelIsDisposed() throws Exception {