Update blum.py

[MOTOR92]

Description
This pull request fixes an issue where the code attempts to concatenate a string with a None value, resulting in a TypeError. Specifically, the method r.get('referralToken') can return None, which cannot be concatenated with a string in Python.

Fix
The solution is to add a check to ensure the value of referralToken exists before attempting to concatenate it with the string. If referralToken is None, the code will handle it appropriately, avoiding the TypeError.

Changes
Added a check for referralToken in the stats method.
Included logging for instances where referralToken is None to aid in debugging.
Impact
This fix prevents the script from crashing due to a TypeError when referralToken is None, ensuring smoother execution and better error handling.