unhandled exception script

Question

Traceback (most recent call last):

File "app.py", line 40, in <module>

File "database_manager.py", line 19, in load_data_to_memory

File "encrypt_decrypt.py", line 11, in decrypt

File "cryptography\fernet.py", line 75, in decrypt

File "cryptography\fernet.py", line 107, in _get_unverified_token_data

cryptography.fernet.InvalidToken

During handling of the above exception, another exception occurred:

Traceback (most recent call last):

File "app.py", line 56, in <module>

TypeError: object of type 'NoneType' has no len()