Fix error on production server

[akircher]

Error opening view group idx-50fe0ec4f5b7b2285fb1dbccd31a31e1 from database drug: {'EXIT', {{case_clause, {[{<<"fields">>, {[{<<"upc">>, <<"asc">>}]}}]}}, [{couch_mrview_util, '-ddoc_to_mrst/2-fun-0-', 2, [{file, "src/couch_mrview_util.erl"}, {line, 65}]}, {lists, foldl, 3, [{file, "lists.erl"}, {line, 1262}]}, {couch_mrview_util, ddoc_to_mrst, 2, [{file, "src/couch_mrview_util.erl"}, {line, 88}]}, {couch_index_server, get_index, 4, [{file, "src/couch_index_server.erl"}, {line, 54}]}, {couch_util, with_db, 2, [{file, "couch_util.erl"}, {line, 443}]}, {couch_mrview, get_info, 2, [{file, "src/couch_mrview.erl"}, {line, 91}]}, {couch_compaction_daemon, maybe_compact_view, 3, [{file, "couch_compaction_daemon.erl"}, {line, 227}]}, {couch_compaction_daemon, maybe_compact_views, 3, [{file, "couch_compaction_daemon.erl"}, {line, 201}]}]}}