Fix NPC shutdown crash (#2971)

Co-authored-by: Metal Gear Sloth <metalgearsloth@gmail.com>

Content.Server/AI/Operators/Sequences/SequenceOperator.cs

@@ -17,9 +17,9 @@ namespace Content.Server.AI.Operators.Sequences
             {
                 return Outcome.Success;
             }
-            
+
             var op = Sequence.Peek();
-            op.TryStartup();
+            op.Startup();
             var outcome = op.Execute(frameTime);
 
             switch (outcome)
@@ -35,10 +35,10 @@ namespace Content.Server.AI.Operators.Sequences
                     op.Shutdown(outcome);
                     Sequence.Clear();
                     return Outcome.Failed;
-                
+
                 default:
                     throw new ArgumentOutOfRangeException();
             }
         }
     }
-}
+}