Make plugin warn when syncing in something that isn't a place

[LPGhatguy]

The plugin tries to destroy the DataModel if you sync in a project that describes a model. That's no good, we should instead catch this case and warn.

Maybe the server should also issue a warning if you serve a non-DataModel project, since that generally doesn't make much sense!

[masteratminecraftpc2]

Piggy

[boatbomber]

Oh, this issue has gotten more important recently. The diff visualizer for sync confirmation errors when syncing a non-place because it assumes it can access .Parent, which fails a security level check.

[steveprogramc]

Protection thanks.

[steveprogramc]

ok let go.