This led to a crash when a cape or skin was not stored on disk.
The function caled skins.save_image and returned that function's lwip image object instead of the expected buffer.
skins.save_image also no longer returns the image object because it's not used anywhere
this was originally implemented because we wanted to delete the oldest images on disk
where 'oldest' means not *used* for the longest time
that's not useful and was never actually implemented, so we don't need this
when using cache.save_hash, an `undefined` skin or cape hash means "do not touch"
while `null` means "overwrite as non-existent"
this was sent to redis after calling /capes/Notch for the first time:
"hmset" "notch" "c" "3f688e0e699b3d9fe448b5bb50a3a288f9c589762b3dae8308842122dcb81" "t" "1429651244222"
"hmset" "notch" "s" "a116e69a845e227f7ca1fdde8c357c8c821ebd4ba619382ea4a1f87d4ae94" "c" "" "t" "1429651244235"
as you can see, the first request stores the c(ape) but does not touch the s(kin), whereas the second request
sets the s(kin) and replaces the c(ape) value
- made sure that get_cape returns a status
- response.js returns 404 if body is empty
- 'X-Storage-Type: undefined' is no longer returned when status is `null`
