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
{
			DesignElement element = module.getElementByID( elementID );
			
			assert element != content;
			if ( element == null )
				module.addElementID( content );
			else
			{
				handler
						.getErrorHandler( )
						.semanticError(
								new DesignParserException(
										new String[]{content.getIdentifier( ),
												element.getIdentifier( )},
										DesignParserException.DESIGN_EXCEPTION_DUPLICATE_ELEMENT_ID ) );
				return false;
			}
		}
		
		container.getSlot( slotID ).add( content );
		
		content.setContainer( container, slotID );
		return true;
	}
	/**
	 * Initializes a report element with "name" and "extends" property.
	 * 
	 * @param attrs
	 *            the SAX attributes object
	 * @param nameRequired