avcodec/parser: fill avctx dimensions if unset

This allows the usage of codecs in builds that have a parser but no decoders
for remuxing scenarios with raw sources.

Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/parser.c

@@ -166,6 +166,10 @@ int av_parser_parse2(AVCodecParserContext *s, AVCodecContext *avctx,
 #define FILL(name) if(s->name > 0 && avctx->name <= 0) avctx->name = s->name
     if (avctx->codec_type == AVMEDIA_TYPE_VIDEO) {
         FILL(field_order);
+        FILL(coded_width);
+        FILL(coded_height);
+        FILL(width);
+        FILL(height);
     }
 
     /* update the file pointer */