Bug 132515 Expression like "Toltal.rank(Tolta.ave(row[a]),ture,Null,1)" is return an error
Description: Add an expression like "Toltal.rank(Tolta.ave(row[a]),ture,Null,1)" is return an error.The nesting "Toltal" seem not to be work. Step to reproduce: 1.new a datasource and dataset 2.drag the dataset to layout veiw for a table 3.set a group on the table 4.Insert a data into the group header with the expression e.g. "Toltal.rank(Tolta.ave(row[a]),ture,Null,1)" Actual result: An error was thrown out Expected result: It should work correctly in order to support some requirments
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/expression/ExpressionProcessor.java
* @throws DataException
	 */
	private void compileBaseExpression(IBaseExpression baseExpression ) throws DataException {
		Context context = Context.enter();
		try {
		if (baseExpression instanceof IConditionalExpression)
		{
			IConditionalExpression condition = (IConditionalExpression) baseExpression;
			IScriptExpression op = condition.getExpression();
			IScriptExpression op1 = condition.getOperand1();
			IScriptExpression op2 = condition.getOperand2();
			if (op != null)
				helper.compileExpression(op.getText(), context);
			if (op1 != null)
				helper.compileExpression(op1.getText(), context);
			if (op2 != null)
				helper.compileExpression(op2.getText(), context);
		}
		else if (baseExpression instanceof IScriptExpression)
		{
			IScriptExpression scriptExpr = (IScriptExpression) baseExpression;
			helper.compileExpression(scriptExpr.getText(), context);
		}}
		 finally {
			Context.exit();
		}
	}
	
	/**
	 * calculate the aggregate object which pass level is 1 and register the