Exception - Attempted to resume pathing action with an invalid skill: 2148073372

I was running a map (Hidden Grotto) when all of a sudden the game froze then this message was displayed

Exception - Attempted to resume pathing action with an invalid skill: 2148073372
object: Metadata/Monsters/MudBurrower/BrambleBurrower@78

the game then closed after i clicked the ok button
went to restart and log back in, but the same message keeps popping up and the game closes again after clicking ok.