wmapro: return early on unsupported condition

Reported-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org
(cherry picked from commit 6652338f43)

Signed-off-by: Reinhard Tartler <siretart@tauware.de>

Conflicts:
	libavcodec/wmaprodec.c

libavcodec/wmaprodec.c

@@ -720,6 +720,7 @@ static int decode_channel_transform(WMAProDecodeCtx* s)
                     if (get_bits1(&s->gb)) {
                         av_log_ask_for_sample(s->avctx,
                                               "unsupported channel transform type\n");
+                        return AVERROR_PATCHWELCOME;
                     }
                 } else {
                     chgroup->transform = 1;