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
acceptCurrentProposal();
					}
					close();
					break;
				case SWT.TAB:
					e.doit = false;
					getShell().setFocus();
					return;
				case SWT.BS:
					
					if (filterStyle != FILTER_NONE) {
						
						if (filterText.length() == 0) {
							return;
						}
						
						filterText = filterText.substring(0, filterText
								.length() - 1);
						asyncRecomputeProposals(filterText);
						return;
					}
					 
					
					
					  
					int pos = getControlContentAdapter().getCursorPosition(getControl());
					
					
					
					if (pos > 0) {