In a web core 1.8.5 this instruction was fine , now i updated webcore 1.9 give me this error !!
It's not clear whether this is code related or JSON related.
From the error, it would appear that your JSON array doesn't contain the value 'RowList'.
I cannot think of another reason as we didn't do changes in WEBLib.JSON between 1.8.5 and 1.9 in this area.