Bug 206850 [Regression] Error pops up when select value for a map or highlight rule to group header row [0302]
model/org.eclipse.birt.report.model.tests/test/org/eclipse/birt/report/model/api/HighlightRuleHandleTest.java
StyleHandle style3 = designHandle.findStyle( "My Style3" ); 
		Iterator highlightRules = style2.highlightRulesIterator( );
		assert ( highlightRules.hasNext( ) );
		HighlightRuleHandle style2Highlight = (HighlightRuleHandle) highlightRules
				.next( );
		assertEquals( DesignChoiceConstants.TEXT_ALIGN_RIGHT, style2Highlight
				.getTextAlign( ) );
		assertEquals( ColorPropertyType.RED, style2Highlight.getColor( )
				.getStringValue( ) );
		assertNull( style2Highlight
				.getProperty( IStyleModel.HIGHLIGHT_RULES_PROP ) );
		
		assertNull( style2Highlight.getProperty( HighlightRule.VALUE2_MEMBER ) );
		StyleHandle style1 = designHandle.findStyle( "My Style1" ); 
		List refs = ( (ReferenceableElement) style1.getElement( ) )
				.getClientList( );
		assertEquals( 1, refs.size( ) );
		BackRef ref1 = (BackRef) refs.get( 0 );
		assertEquals( "My Style2", ref1.getElement( ).getName( ) ); 
		assertEquals( "highlightRules", ref1.getPropertyName( ) ); 
		
		style2Highlight.drop( );
		refs = ( (ReferenceableElement) style1.getElement( ) ).getClientList( );
		assertEquals( 0, refs.size( ) );
		designHandle.getCommandStack( ).undo( );
		refs = ( (ReferenceableElement) style1.getElement( ) ).getClientList( );
		assertEquals( 1, refs.size( ) );
		designHandle.getCommandStack( ).redo( );
		refs = ( (ReferenceableElement) style1.getElement( ) ).getClientList( );
		assertEquals( 0, refs.size( ) );