Bug 127080 [Field Assist] widget disposed error on proposal insertion
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/ContentProposalAdapter.java
scrollbar.addListener(SWT.Selection, this);
				
				getShell().addListener(SWT.Deactivate, this);
				getShell().addListener(SWT.Close, this);
				
				control.addListener(SWT.MouseDoubleClick, this);
				control.addListener(SWT.MouseDown, this);
				control.addListener(SWT.Dispose, this);
				control.addListener(SWT.FocusOut, this);
				
				Shell controlShell = control.getShell();
				controlShell.addListener(SWT.Move, this);
				controlShell.addListener(SWT.Resize, this);
			}
			
			void removeListeners() {
				proposalTable.removeListener(SWT.FocusOut, this);
				ScrollBar scrollbar = proposalTable.getVerticalBar();
				if (scrollbar != null)
					scrollbar.removeListener(SWT.Selection, this);
				getShell().removeListener(SWT.Deactivate, this);
				getShell().removeListener(SWT.Close, this);
				control.removeListener(SWT.MouseDoubleClick, this);
				control.removeListener(SWT.MouseDown, this);
				control.removeListener(SWT.Dispose, this);
				control.removeListener(SWT.FocusOut, this);
				Shell controlShell = control.getShell();
				controlShell.removeListener(SWT.Move, this);
				controlShell.removeListener(SWT.Resize, this);
			}