avoid unknown free variable error in messages

server/leanserver/GameServer/RpcHandlers.lean

@@ -76,6 +76,7 @@ def getLevelByFileName [Monad m] [MonadError m] [MonadEnv m] (fileName : String)
 open Meta in
 /-- Find all messages whose trigger matches the current goal -/
 def findMessages (goal : MVarId) (doc : FileWorker.EditableDocument) : MetaM (Array String) := do
+  goal.withContext do
     let level ← getLevelByFileName doc.meta.mkInputContext.fileName
     let messages ← level.messages.filterMapM fun message => do
       let (declMvars, binderInfo, messageGoal) ← forallMetaBoundedTelescope message.goal message.intros