Rw2Decoder::decodeRawInternal(): actually bailout on unknown version
Rw2Decoder::decodeRawInternal(): actually bailout on unknown version

Highlights unsupported version=6 raws.

LebedevRI/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,LebedevRI/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,LebedevRI/rawspeed,darktable-org/rawspeed,darktable-org/rawspeed,darktable-org/rawspeed