Bug 122419 Masterpage cannot access Data Set properties
If one references a data set property in the master page, i.e. row["title"], then the viewer displays only 'undefined'.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/data/dte/ReportQueryBuilder.java
* A helper function for removing expression collection from stack
		 */
		protected void popExpressions( )
		{
			assert !expressionStack.isEmpty( );
			this.expressions = (Collection) expressionStack.removeLast( );
		}
		protected void pushReportItemQuery( IBaseQueryDefinition query )
		{
			if( this.reportItemQueryStack == null )
			{
				this.reportItemQueryStack = new LinkedList( );
			}
			this.reportItemQueryStack.addLast( query );
		}
		
		protected void popReportItemQuery( )
		{
			assert this.reportItemQueryStack.isEmpty( ) == false;
			this.reportItemQueryStack.removeLast( );
		}
		
		/**
		 * A helper function for adding a query to query stack
		 */
		protected void pushQuery( IBaseTransform query )
		{
			this.queryStack.addLast( query );
		}
		/**