Detect Invalid/Removed Textures, Fonts, Audio, etc.

[Twintop]

Because TIB uses LibSharedMedia, a user can choose a font/texture/audio file to use in the bar that is provided by another addon. If this other addon is removed, the resource is also removed with it. When this happens, the bar will stop functioning in some way -- text not displayed, blank textures, no audio, etc.

Need to add sanity checks around these resources so that if a resource is not available it gracefully changes to a different resource. Also possibly prompt the user that something happened and why.

[Twintop]

Now that there is an easy way to import/export, this is no longer "low priority". Need to address this to prevent breakage between different LibSharedMedia values.

[Twintop]

Had the first reported occurrence of this (via jaerv, on behalf of one of Viklund's subscribers using the import string). Need to do this Soon (no TM).

[Twintop]

Another report of this (Tf in Discord), this time with font not being valid and causing no bar text to show up. This was via importing a configuration.

[Twintop]

Due to addons loading in different orders, there can be false negative matches on textures/fonts/audio seemingly missing but are actually there (just not loaded yet). Need to change where and when this sanity check is applied.