Bug 148747 Design become invalid when I extend a masterpage from Library
The attachment contains a report file and a library file. Reproduce: 1. Deploy the library("lib"), and open the report. 2. Drag Masterpage("page1") from "lib" to report. 3. Reopen the report, it become invalid.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/parser/ReportElementState.java
if ( container.getExtendsElement( ) != null )
		{
			handler
					.getErrorHandler( )
					.semanticWarning(
							new ContentException(
									container,
									slotID,
									content,
									ContentException.DESIGN_EXCEPTION_STRUCTURE_CHANGE_FORBIDDEN ) );
			return false;
		}
		
		if ( !slotInfo.isMultipleCardinality( )
				&& container.getSlot( slotID ).getCount( ) > 0 )
		{
			handler.getErrorHandler( ).semanticError(
					new ContentException( container, slotID,
							ContentException.DESIGN_EXCEPTION_SLOT_IS_FULL ) );
			return false;
		}
		
		
		addToNamespace( content );
		Module module = handler.getModule( );
		
		
		long elementID = content.getID( );
		if ( elementID > 0 )