libavfilter/lavfutils: remove useless NULL check on codec context

The code would crash before if it was NULL

Fixes CID733804
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/lavfutils.c

@@ -85,8 +85,7 @@ int ff_load_image(uint8_t *data[4], int linesize[4],
     av_image_copy(data, linesize, (const uint8_t **)frame->data, frame->linesize, *pix_fmt, *w, *h);
 
 end:
-    if (codec_ctx)
-        avcodec_close(codec_ctx);
+    avcodec_close(codec_ctx);
     if (format_ctx)
         avformat_close_input(&format_ctx);
     av_freep(&frame);