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
{
		return getActiveReportEditor( true );
	}
	/**
	 * Returns the current active report editor in current active page or
	 * current active workbench.
	 * 
	 * @param activePageOnly
	 *            If this is true, only search the current active page, or will
	 *            search all pages in current workbench, returns the first
	 *            active report or null if not found.
	 * @return the current active report editor, or null if no report editor is
	 *         active.
	 */
	public static FormEditor getActiveReportEditor( boolean activePageOnly )
	{
		IWorkbenchWindow window = PlatformUI.getWorkbench( )
				.getActiveWorkbenchWindow( );
		if ( window != null )
		{
			if ( activePageOnly )
			{
				IWorkbenchPage pg = window.getActivePage( );
				if ( pg != null )
				{
					IEditorPart editor = pg.getActiveEditor( );
					if ( editor != null )
					{
						if ( editor instanceof IReportEditor )
						{