[BUG] Can no longer run multiple instances MM [#21818]

[MikeGahrns]

I just installed 2024.2.0.3171 that came out today, and could not start a second instance of MM.

This seems like a regression, because I have run multiple instances in the recent past.

I doubled checked and confirmed in Options that "Allow just one instance of MM" is unchecked.

[Lowlander]

I was able to reproduce on 3171, and no issue with 3167. Tracking as: https://www.ventismedia.com/mantis/view.php?id=21818