Server Error when approving a user's friend request

We are using the Friend Requests plugin by ColdTricks IT Solutions. However, we found a glitch in which when a user gets a friend request and they approve that user to be their friend then the user who accepts the friend request is shown a Error 500 from the plugin. 

Can you guys help me out as to what is wrong? I have a feeling because we are running Elgg 1.8.16 that the code could have changed? :S