avcodec/utvideodec: move allocation to the end of init

Fixes: mem leak
Fixes: 62164/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_UTVIDEO_fuzzer-6666804266926080

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

libavcodec/utvideodec.c

@@ -1012,10 +1012,6 @@ static av_cold int decode_init(AVCodecContext *avctx)
         return AVERROR_INVALIDDATA;
     }
 
-    c->buffer = av_calloc(avctx->width + 8, c->pro?2:1);
-    if (!c->buffer)
-        return AVERROR(ENOMEM);
-
     av_pix_fmt_get_chroma_sub_sample(avctx->pix_fmt, &h_shift, &v_shift);
     if ((avctx->width  & ((1<<h_shift)-1)) ||
         (avctx->height & ((1<<v_shift)-1))) {
@@ -1063,6 +1059,10 @@ static av_cold int decode_init(AVCodecContext *avctx)
         return AVERROR_INVALIDDATA;
     }
 
+    c->buffer = av_calloc(avctx->width + 8, c->pro?2:1);
+    if (!c->buffer)
+        return AVERROR(ENOMEM);
+
     return 0;
 }