Fix too small buffer, reported by  David Binderman.
Fix too small buffer, reported by  David Binderman.

darktable-org/rawspeed,klauspost/rawspeed,LebedevRI/rawspeed,mgehre/rawspeed,darktable-org/rawspeed,anarsoul/rawspeed,darktable-org/rawspeed,klauspost/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,anarsoul/rawspeed,anarsoul/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,mgehre/rawspeed,LebedevRI/rawspeed,LebedevRI/rawspeed