Added a comment to remind myself how to correctly clean up iwa.

source/object.cpp

@@ -40,6 +40,8 @@ struct ObjectPtrAllocationsChecker
                 }
 #endif
             }
+
+            // did you call instance->requestQuit() and then instance->getMainTaskLoop().runUntilDone()?
             std::cerr.flush();
             MIJIN_TRAP();
         }