Distinguish between non-recognized file type and error when assessing file type

[ahayes]

When a user uploads a file to a attach to a Nunaliit atlas document via a schema attribute of type "file", Nunaliit will attempt to figure out what type of file it is. If it recognizes the type of file as one that it can perform enhanced processing on, such as video, audio, image, PDF, GPX, etc. then it will proceed with those special workflows. By design, if it does not recognize the type of file, it will proceed to attach it and display a generic "document" icon in place of a video/image/PDF thumbnail, audio icon, or other flair. This allows for atlases to accommodate unexpected files which could be stored and retrieved. At a later date, files could be reprocessed if additional support for the formatted were warranted. This is how GPX file support support came to be, for example.

Unfortunately, if an exception occurs while trying to identify the file type, Nunaliit may erroneously conclude that the file was not a recognized type and proceed without proper processing. This would result in unexpected behaviour such as a generic icon being displayed in place of a thumbnail, a video or audio file that won't play in the browser because it was not transcoded to a supported format, or other issues depending on the file type. Additionally, No plugin found for uploaded file class: null errors may be seen in Nunaliit's log files.

Nunaliit should be improved to distinguish between non-recognized file type and error when assessing file type.