[Revscriptsys] fix crash introduced in #4742

[EvilHero90]

Pull Request Prelude

• [x] I have followed proper The Forgotten Server code styling.
• [x] I have read and understood the contribution guidelines before making this PR.
• [x] I am aware that this PR may be closed if the above-mentioned criteria are not fulfilled.

Changes Proposed

There was a missing check to see if the pointer had a valid map before trying to access it, that's why there was an out of range violation which crashed the server when trying to set aid/uid/pos to either Actions or MoveEvents

Issues addressed: fixes #4748