Bug 124600 delete Grid Column causes NPE thrown out in error log
steps to reproduce: - insert a 3*3 grid - delete grid columns one by one expected behavior: - these operations should completed without any error. actual behavior: - after i deleted the 3rd column, NPE was thrown out in error log.
UI/org.eclipse.birt.report.designer.core/src/org/eclipse/birt/report/designer/util/DNDUtil.java
return pasteParameterGroup( commandType, transferSource,
					(ParameterGroupHandle) newContainer );
		}
		else if ( transferSource instanceof DesignElementHandle )
		{
			return new PasteCommand( (DesignElementHandle) transferSource,
					newContainer, position, isCut );
		}
		else if ( transferSource instanceof IDesignElement )
		{
			return new PasteCommand( (IDesignElement) transferSource,
					newContainer, position );
		}
		return null;
	}
	protected static Command pasteParameterGroup( String commandType,
			Object childGroup, ParameterGroupHandle targetGroup )
	{
		CompoundCommand commands = new CompoundCommand( );
		ParameterGroupHandle childHandle = null;
		if ( childGroup instanceof ParameterGroupHandle )
		{
			childHandle = (ParameterGroupHandle) childGroup;
		}
		else if ( DEUtil.isParameterGroup( childGroup ) )
		{
			childHandle = (ParameterGroupHandle) ( (IDesignElement) childGroup )
					.getHandle( SessionHandleAdapter.getInstance( )
							.getReportDesignHandle( ).getModule( ) );
		}