[EventDispatcher] Fixed #12845 adding a listener to an event that is currently being dispatched

[EventDispatcher] Fixed adding listener when event is currently being dispatched

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #12845
| License       | MIT