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
}
	/**
	 * Gets EditPartViewer in layout editor.
	 * 
	 * @return the EditPartViewer in layout editor, or null if not found.
	 */
	public static EditPartViewer getLayoutEditPartViewer( )
	{
		IEditorPart part = PlatformUI.getWorkbench( )
				.getActiveWorkbenchWindow( )
				.getActivePage( )
				.getActiveEditor( );
		AbstractMultiPageEditor reportEditor = null;
		if ( part instanceof AbstractMultiPageEditor )
		{
			reportEditor = (AbstractMultiPageEditor) part;
		}
		else if ( part instanceof IReportEditor )
		{
			IEditorPart activeEditor = ( (IReportEditor) part ).getEditorPart( );
			if ( activeEditor instanceof AbstractMultiPageEditor )
			{
				reportEditor = (AbstractMultiPageEditor) activeEditor;
			}
		}
		if ( reportEditor == null
				|| !( reportEditor.getActivePageInstance( ) instanceof GraphicalEditorWithFlyoutPalette ) )
		{
			return null;
		}