Bug 152430 Key can modify to empty string
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/command/PropertyCommand.java
propDefn );
			if ( list != null )
				return;
			
			ArrayList inherited = (ArrayList) element.getProperty( module,
					propDefn );
			list = new ArrayList( );
			if ( inherited != null )
			{
				for ( int i = 0; i < inherited.size( ); i++ )
					list.add( ( (IStructure) inherited.get( i ) ).copy( ) );
			}
			
			PropertyRecord propRecord = new PropertyRecord( element, propDefn,
					list );
			getActivityStack( ).execute( propRecord );
			return;
		}
		
		Structure struct = (Structure) element.getLocalProperty( module,
				propDefn );
		if ( struct != null )
			return;
		
		Structure inherited = (Structure) element
				.getProperty( module, propDefn );
		if ( inherited != null )
		{
			IStructure copy = inherited.copy( );
			PropertyRecord propRecord = new PropertyRecord( element, propDefn,