avcodec/magicyuvenc: Fix memleak upon init failure

If an error happens during init after an allocation has succeeded,
the already allocated data leaked up until now. Fix this by setting the
FF_CODEC_CAP_INIT_CLEANUP flag.

Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavcodec/magicyuvenc.c

@@ -587,4 +587,5 @@ AVCodec ff_magicyuv_encoder = {
                           AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUV444P, AV_PIX_FMT_YUVA444P, AV_PIX_FMT_GRAY8,
                           AV_PIX_FMT_NONE
                       },
+    .caps_internal    = FF_CODEC_CAP_INIT_CLEANUP,
 };