Handle Unsupported Subject Media: Subject Stuck when loading text file

[wgranger]

The MHS iPads at the Adler are stuck on the "Subject Loading" spinner whenever accessing MHS. However, this only occurs when logged in as AdlerMHS, which leads me to believe it has something to do with the subject queue/having seen all subjects. The app fetches images fine when another museum-role user is logged into MHS.

I am also seeing the following error, which arises from NativeModules in the NativeImage component. Error occurs when logged in as AdlerMHS and accessing the MHS project.

[wgranger]

Upon further investigation, this is an issue with a .txt file in the subject set. I'll retitle this issue, but I'm not sure how we want to handle the accidental inclusion of a text file in a subject set.