The current code assumes that a display UUID can be created with the
stored ID, but that's not always the case, e.g. when the user doesn't
have the display connected. As such, we need to null check this, and
fall back to the invalid ID (0) when the ID cannot be migrated.
The current code also only migrates on source creation, which yields
weird behaviour where if the user opens properties and then cancels it
would still show the first display, but only for the session. This is
why the code was factored out of the creation function and now is always
used when an ID needs to be acquired from OBS Data settings, including
when the source is updated.
Typedef pointers are unsafe. If you do:
typedef struct bla *bla_t;
then you cannot use it as a constant, such as: const bla_t, because
that constant will be to the pointer itself rather than to the
underlying data. I admit this was a fundamental mistake that must
be corrected.
All typedefs that were pointer types will now have their pointers
removed from the type itself, and the pointers will be used when they
are actually used as variables/parameters/returns instead.
This does not break ABI though, which is pretty nice.
