avcodec/012v: Order operations for odd size handling

Fixes: out of array access
Fixes: 48567/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ZERO12V_fuzzer-6714182078955520.fuzz
Fixes: 48567/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ZERO12V_fuzzer-6698145212137472.fuzz

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

libavcodec/012v.c

@@ -131,8 +131,8 @@ static int zero12v_decode_frame(AVCodecContext *avctx, AVFrame *pic,
             u = x/2 + (uint16_t *)(pic->data[1] + line * pic->linesize[1]);
             v = x/2 + (uint16_t *)(pic->data[2] + line * pic->linesize[2]);
             memcpy(y, y_temp, sizeof(*y) * (width - x));
-            memcpy(u, u_temp, sizeof(*u) * (width - x + 1) / 2);
-            memcpy(v, v_temp, sizeof(*v) * (width - x + 1) / 2);
+            memcpy(u, u_temp, sizeof(*u) * ((width - x + 1) / 2));
+            memcpy(v, v_temp, sizeof(*v) * ((width - x + 1) / 2));
         }
 
         line_end += stride;