Bug 154828 Item from library contant user properties can't delete
Details: Item from library contant user properties can't delete Step: 1.New a library. 2.Add a label and add a user properites. 3.Public the library. 4.New a report design and use the library 5.Drop the label from library explorer into layout. 6.Try to delete it. Actual result: The label from library contant user properties can't be delete. Exception reuslt: The label can be delete.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/command/ContentCommand.java
if ( hasDescendents( content, slotID ) )
		{
			throw new ContentException( element, slotID,
					ContentException.DESIGN_EXCEPTION_HAS_DESCENDENTS );
		}
		
		ContentRecord dropRecord = new ContentRecord( module, element, slotID,
				content, false );
		ActivityStack stack = getActivityStack( );
		stack.startFilterEventTrans( dropRecord.getLabel( ) );
		try
		{
			doDelectAction( content, unresolveReference );
		}
		catch ( SemanticException ex )
		{
			stack.rollback( );
			throw ex;
		}
		
		stack.execute( dropRecord );
		stack.commit( );
	}
	/**
	 * Changes derived elements to derive from the parent (if any) instead.
	 * 
	 * @param obj
	 *            the element to clean up