AVFormat Muxer : Don't create AVStreams for unsupported ES types.

Currently, the libavformat based muxer supports audio and video streams
properly. Subtitle muxing is still a work-in-progress. Till those are
verified to work as well, we need to ensure that we don't create AVStreams
with invalid codec type.
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>
(cherry picked from commit e276b648)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/demux/avformat/mux.c

@@ -214,6 +214,12 @@ static int AddStream( sout_mux_t *p_mux, sout_input_t *p_input )
     p_input->p_sys = malloc( sizeof( int ) );
     *((int *)p_input->p_sys) = p_sys->oc->nb_streams;
 
+    if( p_input->p_fmt->i_cat != VIDEO_ES && p_input->p_fmt->i_cat != AUDIO_ES)
+    {
+        msg_Warn( p_mux, "Unhandled ES category" );
+        return VLC_EGENERIC;
+    }
+
     stream = av_new_stream( p_sys->oc, p_sys->oc->nb_streams);
     if( !stream )
     {
@@ -258,8 +264,6 @@ static int AddStream( sout_mux_t *p_mux, sout_input_t *p_input )
         codec->time_base.num = p_input->p_fmt->video.i_frame_rate_base;
         break;
 
-    default:
-        msg_Warn( p_mux, "Unhandled ES category" );
     }
 
     codec->bit_rate = p_input->p_fmt->i_bitrate;