Need help! I don't know how to express if statement, if original string is empty and integer is 0?

Question

https://code.sololearn.com/c3I9EC5pG8i9/?ref=app
Code is practicaly correct, I just don't know how to express this additional if statement. In my code this integer is as denominator. So I have problem.

Answer 1

Mark the code or refer to a line.

Answer 2

Line 23

Answer 3

Thanks for answer, but I like that it will return "". Because there must be return string not statement.