adpcmenc: check return value of avcodec_alloc_frame()

Signed-off-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/adpcmenc.c

@@ -137,7 +137,8 @@ static av_cold int adpcm_encode_init(AVCodecContext *avctx)
     }
 
     avctx->coded_frame = avcodec_alloc_frame();
-    avctx->coded_frame->key_frame= 1;
+    if (!avctx->coded_frame)
+        goto error;
 
     return 0;
 error: