Make use of Impossible States approach

http://fsharpforfunandprofit.com/posts/designing-with-types-making-illegal-states-unrepresentable/#series-toc

to fix the smothering of the Dropbox file with little or no contents.

Also see Feldman's video - https://www.youtube.com/watch?v=IcgmSRJHu_8

Start by reading the linked “Impossible States” article and Feldman video, then inspect how elmBox handles Dropbox files with little or no contents. Reproduce the smothering behavior and define the expected handling for empty files; the issue is complete when that behavior is corrected and verified.

Written by the indexing model from the issue text.