avcodec/wavpacl: Fix runtime error: left shift of negative value -1

Fixes: 607/clusterfuzz-testcase-5108792465293312

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/targets/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/wavpack.c

@@ -682,7 +682,7 @@ static int wavpack_decode_block(AVCodecContext *avctx, int block_no,
     s->hybrid_bitrate =   s->frame_flags & WV_HYBRID_BITRATE;
     s->post_shift     = bpp * 8 - orig_bpp + ((s->frame_flags >> 13) & 0x1f);
     s->hybrid_maxclip =  ((1LL << (orig_bpp - 1)) - 1);
-    s->hybrid_minclip = ((-1LL << (orig_bpp - 1)));
+    s->hybrid_minclip = ((-1UL << (orig_bpp - 1)));
     s->CRC            = bytestream2_get_le32(&gb);
 
     // parse metadata blocks