Bug 125955 [Field Assist] - StringIndexOutOfBoundsException when backspacing out of a filter
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/ContentProposalAdapter.java
return null;
		}
		/*
		 * Select the proposal at the given index.
		 */
		private void selectProposal(int index) {
			Assert
					.isTrue(index >= 0,
							"Proposal index should never be negative"); 
			if (!isValid() || proposals == null || index >= proposals.length)
				return;
			proposalTable.setSelection(index);
			proposalTable.showSelection();
			showProposalDescription(proposals[index].getDescription());
		}
		/**
		 * Opens this ContentProposalPopup. This method is extended in order to
		 * add the control listener when the popup is opened and to invoke the
		 * secondary popup if applicable.
		 * 
		 * @return the return code
		 * 
		 * @see org.eclipse.jface.window.Window#open()
		 */
		public int open() {
			addControlListener();
			int value = super.open();
			showProposalDescription(getSelectedProposal().getDescription());
			return value;
		}