What can I do to fix this?

Blueprint Runtime Error: “Accessed None trying to read property Player Character BP”. Node: Set Percent Graph: Increase Stamina Function: Increase Stamina Blueprint: BPC_PlayerStats
Whenever stop playing my game it shows this error, I’ve looked online and found an old forum post about the exact same tutorial I am following, but the solution that was on there just made another problem, so I don’t know what to do.

This is my code that I’ve sourced the problem to.

The reference is null, not pointing to a specific actor instance. Could you show where you Set Percent?