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
ScrollBar vbar = scomp.getVerticalBar( );
		if ( vbar != null )
		{
			Rectangle clientArea = scomp.getClientArea( );
			int increment = clientArea.height - 5;
			vbar.setPageIncrement( increment );
		}
	}
	private static boolean isWrapControl( Control c )
	{
		if ( c instanceof Composite )
		{
			return ( (Composite) c ).getLayout( ) instanceof ILayoutExtension;
		}
		return ( c.getStyle( ) & SWT.WRAP ) != 0;
	}
	/**
	 * Returns table editpart.
	 * 
	 * @param editParts
	 *            a list of editpart
	 * @return the current selected table editpart, null if no table editpart,
	 *         more than one table, or other non-table editpart. Cell editpart
	 *         is also a type of table editpart.
	 */
	public static TableEditPart getTableEditPart( List editParts )
	{
		if ( editParts == null || editParts.isEmpty( ) )
			return null;
		int size = editParts.size( );