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
}
			if ( part == null )
			{
				part = currentEditPart;
			}
			
			if ( currentEditPart == null
					|| currentEditPart != null
					&& part != currentEditPart )
			{
				return null;
			}
		}
		return part;
	}
	/**
	 * Tests if the specified element is on the given tree viewer
	 * 
	 * @param treeViewer
	 *            the tree viewer
	 * @param element
	 *            the element
	 * 
	 * @return true if the element is on the tree, or false else.
	 */
	public static boolean containElement( AbstractTreeViewer treeViewer,
			Object element )
	{
		ITreeContentProvider provider = (ITreeContentProvider) treeViewer.getContentProvider( );
		Object input = treeViewer.getInput( );