[Physics] Fix exporting with 3D disabled

[AThousandShips]

Regression from:

• Disable registering 3D physics types when 3D is disabled #79185

Unsure if these are all the relevant areas that need guarding (and the test side is a bit broken already with templates, will check more later about testing and exported projects in total, but that's not caused by these changes)

The physics server simply won't work and can't be used when not enabled or created, we could add some kind of dummy server but I think that's a lower priority thing, this makes it possible to export with 3D disabled again

An alternative would also be to simply revert #79185 but I think it has its value

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• Fixes: The export template compiled with "disable_3d=true" failed to start. #88666

[AThousandShips]

Found another place where this is needed, will do another sweep

[akien-mga]

Thanks!

[AThousandShips]

Thank you!