avcodec/vc1dec: Fix memleak upon allocation error

ff_vc1_decode_init_alloc_tables() had one error path that forgot to free
already allocated buffers; these would then be overwritten on the next
allocation attempt (or they would just not be freed in case this
happened during init, as the decoders for which it is used do not have
the FF_CODEC_CAP_INIT_CLEANUP set).

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
(cherry picked from commit 98060a198e)

libavcodec/vc1dec.c

@@ -384,7 +384,7 @@ av_cold int ff_vc1_decode_init_alloc_tables(VC1Context *v)
     if (s->avctx->codec_id == AV_CODEC_ID_WMV3IMAGE || s->avctx->codec_id == AV_CODEC_ID_VC1IMAGE) {
         for (i = 0; i < 4; i++)
             if (!(v->sr_rows[i >> 1][i & 1] = av_malloc(v->output_width)))
-                return AVERROR(ENOMEM);
+                goto error;
     }
 
     ret = ff_intrax8_common_init(s->avctx, &v->x8, &s->idsp,