JWTAuth::validate_refresh_token() causes PHP warnings

[sun]

Problem

• The plugin sometimes triggers PHP warnings (2,164 times in ~1.5 months), because it cannot find the user-provided refresh token in the user account (in order to validate it):

Probable Cause

• The refresh token expired and has been removed from the user account already.

Proposed solution

• Debug and fix the code to not attempt to access an array key that does not exist.

[sun]

Sorry, turns out the warning is actually happening in debugging code we added to our copy.