Deleting BP instances that have dynamic delegate bindings with other actors can cause those other actors to have stale actor desc references

The message can be resolved by resaving the actor desc.

1. Create a world partition map
2. Create an actor BP (henceforth referred to as A), add a variable of type actor object reference, and make that variable instance editable
3. In A's event graph, add an event node from the above variable (such as On Actor Begin Overlap), and attach some other node to the execution pin
4. Place an instance of A in the level
5. Place an instance of any other actor in the level, such as a cube
6. Set the variable you made on A to the cube
7. Save the level
8. Delete the instance of A from the level
9. Save
10. Open a different level
11. Re-open the original level
12. Observe that map check will fail with an error message like: "Actor .../SomeMap.Cube has an invalid reference to SomeGUID"