Bug 121687 Exception throws when export data in table which inside a grid cell.
Description: Exception throws when export data in table which inside a grid cell. Steps to reproduce: 1. insert a grid. 2. insert one table to one grid cell. 3. insert another table to the other grid cell. 4. export data in two tables. Expected result: Data are exported. Actual result: Exception in: ReportEngineService.getMetaData( )
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/parser/EngineIRVisitor.java
protected MapRuleDesign createMapRule( MapRuleHandle handle,
			String defaultStr )
	{
		MapRuleDesign rule = new MapRuleDesign( );
		rule.setExpression( handle.getOperator( ), handle.getValue1( ), handle
				.getValue2( ) );
		rule.setDisplayText( handle.getDisplayKey( ), handle.getDisplay( ) );
		String testExpr = handle.getTestExpression( );
		if ( testExpr != null && testExpr.length( ) > 0 )
		{
			rule.setTestExpression( testExpr );
		}
		else if ( ( defaultStr != null ) && defaultStr.length( ) > 0 )
		{
			rule.setTestExpression( defaultStr );
		}
		else
		{
			
			return null;
		}
		ConditionalExpression condExpr = new ConditionalExpression( rule
				.getTestExpression( ),
				toDteFilterOperator( rule.getOperator( ) ), rule.getValue1( ),
				rule.getValue2( ) );
		rule.setConditionExpr( condExpr );
		return rule;
	}
	/**
	 * Checks if a given style is in report's style list, if not, assign a