Bug 132798 [Field Assist] - Pressing Backspace at offset 0 should not reload field assist popup
N20060322-0010. After migrating the Find/Replace dialog to the new field assist support I found the following blooper: pressing the Backspace key at offset 0 reloads the field assist popup. Test Case: 1. in a text editor press Ctrl+F 2. enable regex search 3. in the Find filed press Ctrl+Space 4. continuously press Backspace ==> each time the proposal list is reloaded.
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/ContentProposalAdapter.java
*            no content proposal is available.
	 * @param keyStroke
	 *            the keystroke that will invoke the content proposal popup. If
	 *            this value is <code>null</code>, then proposals will be
	 *            activated automatically when any of the auto activation
	 *            characters are typed.
	 * @param autoActivationCharacters
	 *            An array of characters that trigger auto-activation of content
	 *            proposal. If specified, these characters will trigger
	 *            auto-activation of the proposal popup, regardless of whether
	 *            an explicit invocation keyStroke was specified. If this
	 *            parameter is <code>null</code>, then only a specified
	 *            keyStroke will invoke content proposal. If this parameter is
	 *            <code>null</code> and the keyStroke parameter is
	 *            <code>null</code>, then all alphanumeric characters will
	 *            auto-activate content proposal.
	 */
	public ContentProposalAdapter(Control control,
			IControlContentAdapter controlContentAdapter,
			IContentProposalProvider proposalProvider, KeyStroke keyStroke,
			char[] autoActivationCharacters) {
		super();
		
		Assert.isNotNull(control);
		Assert.isNotNull(controlContentAdapter);
		this.control = control;
		this.controlContentAdapter = controlContentAdapter;
		
		this.proposalProvider = proposalProvider;
		this.triggerKeyStroke = keyStroke;