Comment 2 for bug 1713598

This seems to be the the reason of the error here
https://mahara.org/interaction/forum/topic.php?id=8030&offset=0&limit=10#post32239

But as the error doesn't mention where the error stems from in the code it will a matter of trying to find where we set up variables as strings then try and treat them as arrays by assigning something to them in the array way