avcodec/vqavideo: reset accounting on error

Fixes: Timeout (same growing chunk is decoded to failure repeatedly)
Fixes: 42582/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VQA_fuzzer-6531195591065600

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

libavcodec/vqavideo.c

@@ -608,13 +608,14 @@ static int vqa_decode_frame_pal8(VqaContext *s, AVFrame *frame)
         if (s->partial_countdown <= 0) {
             bytestream2_init(&s->gb, s->next_codebook_buffer, s->next_codebook_buffer_index);
             /* decompress codebook */
-            if ((res = decode_format80(s, s->next_codebook_buffer_index,
-                                       s->codebook, s->codebook_size, 0)) < 0)
-                return res;
+            res = decode_format80(s, s->next_codebook_buffer_index,
+                                  s->codebook, s->codebook_size, 0);
 
             /* reset accounting */
             s->next_codebook_buffer_index = 0;
             s->partial_countdown = s->partial_count;
+            if (res < 0)
+                return res;
         }
     }