dfa: replace redundant check by assert

The values are checked in the wraper function used to call this code.

This was introduced by: ee715f49a0

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/dfa.c

@@ -20,6 +20,7 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#include "libavutil/avassert.h"
 #include "avcodec.h"
 #include "bytestream.h"
 
@@ -36,12 +37,13 @@ typedef struct DfaContext {
 static av_cold int dfa_decode_init(AVCodecContext *avctx)
 {
     DfaContext *s = avctx->priv_data;
-    int ret;
 
     avctx->pix_fmt = PIX_FMT_PAL8;
 
-    if ((ret = av_image_check_size(avctx->width, avctx->height, 0, avctx)) < 0)
-        return ret;
+    if (!avctx->width || !avctx->height)
+        return AVERROR_INVALIDDATA;
+
+    av_assert0(av_image_check_size(avctx->width, avctx->height, 0, avctx) >= 0);
 
     s->frame_buf = av_mallocz(avctx->width * avctx->height + AV_LZO_OUTPUT_PADDING);
     if (!s->frame_buf)