UAIPerceptionSystem::Tick() has a chance of not being called after level reloading

UAIPerceptionSystem::Tick() is not called after level reloading.

When Debugging, UAIPerceptionSystem::CurrentTime is always 0, and UAIPerceptionSystem::SourcesToRegister always contains sources to register without registering them.

It is worth noting that in these cases the first element of the SourcesToRegister array has source STALE; when the Perception System is correctly working instead, at the first call of UAIPerceptionSystem::PerformSourceRegistration() the first element of the array is the SpectatorPawn (tests were made using the default class, not an inherited one).

1. Download the attached Project  "[Link Removed]"
2. Right click UProject, and Generate Visual Studio Project files.
3. Open the Project, Navigate to ThirdPersonBP->Maps,  and launch Third Person Example Map.
4. Press PIE.
5. The AI Character will move to the player, upon reaching the player, the level will re-load.
6. After doing this for some time.  (up to 50 reloads)

Results: The level is reloaded but the perception system is not working.

Expected: The perception systems should continue to work as usual.