Added a try-catch in order to avoid TypeError: only integer scalar a…

[pacocp]

…rrays can be converted to a scalar index exception in readFlowFile.py

Hi! Thank you very much for this amazing example for reading .flo files.

In order to control the exception described in the title with the code you have as a comment, I have added a try-catch exception controller therefore the user don't have to change the code, it would try both ways automatically.

Thank you very much again! 😄