[core] Always store pet ID when saving pet info

[WinterSolstice8]

I affirm:

• I understand that if I do not agree to the following points by completing the checkboxes my PR will be ignored.
• I understand I should leave resolving conversations to the LandSandBoat team so that reviewers won't miss what was said.
• I have read and understood the Contributing Guide and the Code of Conduct.
• I have tested my code and the things my code has changed since the last commit in the PR and will test after any later commits.

What does this pull request do?

Apparently zoning with an automaton caused a fire elemental to appear because it's pet ID was set to zero.

Steps to test these changes

Zone with an automaton and keep the automaton.

[MowFord]

I think you need more than just the petid though?

I made this PR to resolve the fire elemental when zoning

There was a crash condition that is unrelated to the fix in that PR.