Error Handling - Internal Server Error

[pubmania]

If the period of submission is not on the CSV user gets "Internal Server Error". This is not harmful in anyway but perhaps it can be improved with better error handling where user can be made aware that there is no entry in the CSV that matches the period of submission.

This also applies to data in decimals. It results in "Internal Server Error" but if code can be modified to make user aware that the CSV has decimal values which are not allowed, it will be helpful.

I was wondering if there can be a landing page to redirect the errors or even as a prompt then it wont display "Internal Server Error" because it is not server error but user data is incorrect.

[pubmania]

I have changed code on my fork to include very basic error handling for the CSV submission stage: