.appcache files crash erica

According to #52 the .appcache extension should support setting up the proper mime type. But if I have a .appcache file in my directory then erica (built from git source) crashes:

erica push http://admin:password@localhost:5984/expenses
==> ExpenseTracker (push)
ERROR: push failed while processing /var/www/ExpenseTracker: {'EXIT',{badarg,[{couchbeam,save_doc,4,
[{file,"src/couchbeam.erl"},{line,587}]},
{erica_push,do_push,4,
[{file,"src/erica_push.erl"},{line,91}]},
{erica_push,push2,3,[{file,"src/erica_push.erl"},{line,53}]},
{erica_push,push1,3,[{file,"src/erica_push.erl"},{line,44}]},
{erica_core,run_modules,4,
[{file,"src/erica_core.erl"},{line,98}]},
{erica_core,execute,4,
[{file,"src/erica_core.erl"},{line,68}]},
{erica,main,1,[{file,"src/erica.erl"},{line,12}]},
{escript,run,2,[{file,"escript.erl"},{line,747}]}]}}

Reproduce the failure by running erica push on a directory containing a .appcache file, then inspect src/couchbeam.erl:587 and src/erica_push.erl:91 along with issue #52. Done means the push completes without crashing and the .appcache file receives the intended MIME-type handling.

Written by the indexing model from the issue text.