avcodec/wmalosslessdec: deallocate uninitialized frame on decode_tilehdr() failure

Fixes use of uninitialized memory
partly fixes: msan_uninit-mem_7f7834b6a530_6473_luckynight-partial.wma
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/wmalosslessdec.c

@@ -1040,6 +1040,7 @@ static int decode_frame(WmallDecodeCtx *s)
     /* decode tile information */
     if ((ret = decode_tilehdr(s))) {
         s->packet_loss = 1;
+        av_frame_unref(s->frame);
         return ret;
     }