Bug 175664 [Mac] Unexpected internal exception occurs when invoke expression builder
Description: There are two problems: 1. "fx" button (Click this button to invoke Expression Builder) could not be displayed correctly, nothing displayed in the button. 2. Click on the button, an unexpected internal exception occurs. Version:2.2.0.v20070205 Steps to reproduce: 1.Insert a Data item to the layout. Click "fx" button to invoke the expression builder, although on Mac "fx" button could not display correctly. Error log: Argument cannot be null Plug-in Provider: Eclipse.org Plug-in Name: BIRT Designer UI Plug-in ID: org.eclipse.birt.report.designer.ui Error Code: Error.GUIException.invokedByUnexpectedException Error Message:Argument cannot be null
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/internal/ui/util/UIUtil.java
{
				GroupDialog dialog = new GroupDialog( getDefaultShell( ),
						GroupDialog.GROUP_DLG_TITLE_NEW );
				
				dialog.setInput( groupHandle );
				if ( dialog.open( ) == Window.CANCEL )
				{
					return false;
				}
			}
			return true;
		}
		return false;
	}
	/**
	 * Gets the first selected edit part in layout editor. Whenever the user has
	 * deselected all edit parts, the contents edit part should be returned.
	 * 
	 * @return the first selected EditPart or root edit part
	 */
	public static EditPart getCurrentEditPart( )
	{
		EditPartViewer viewer = getLayoutEditPartViewer( );
		if ( viewer == null )
			return null;
		IStructuredSelection targets = (IStructuredSelection) viewer.getSelection( );
		if ( targets.isEmpty( ) )
			return null;
		return (EditPart) targets.getFirstElement( );