TypeError: null is not an object (evaluating 'constr.toString().match(self.rx_function)')

Hi, I have this issue only on some old version of iPad. The issue is on line 458:

cnName = constr.toString().match(self.rx_function)[1];

I don't know if it's the best solution, but I solved in that way:

cnName = constr.toString().match(self.rx_function) ? [1] : null;