Bug 147377 [Field Assist] - open proposal popup should close when there are no valid proposals left
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/ContentProposalAdapter.java
* Record the control's cursor position.
	 */
	private void recordCursorPosition() {
		if (isValid()) {
			insertionPos = getControlContentAdapter()
					.getCursorPosition(control);
		}
	}
	
	/*
	 * Get the proposals from the proposal provider. 
	 * Gets all of the proposals without doing any filtering.
	 */
	private IContentProposal[] getProposals() {
		if (proposalProvider == null || !isValid()) {
			return null;
		}
		int position = insertionPos;
		if (position == -1) {
			position = getControlContentAdapter().getCursorPosition(
					getControl());
		}
		String contents = getControlContentAdapter().getControlContents(
				getControl());
		IContentProposal[] proposals = proposalProvider.getProposals(
				contents, position);
		return proposals;
	}
}