Fast Formula compilation error - APP-FF-33005 The local variable was used before being initialized

APP-FF-33005: The local variable XXUDC_FURN_MAINT_ALLOW was used before being initialized

Cause:        The variable named in the error message is being used before any value has been assigned to it, so it has no meaningful value. 

Action:        Please ensure variables have been assigned to before using them.

I am using a user defined function in my Fast formula. However I am getting the above message.

The function works fine without any issues. But the fast formula gives errors:

/*****************************************************************************
                           UDC ERP: HRMS System
                  Furniture Maintenance Input Validation Formula

Globals                :None
Balances               :None
User Defined Functions :XXUDC_FURN_MAINT_ALLOW, XXUDC_FURN_MAINT_VALUE