ffmpegcodecmap: don't create dummy codec data for FLAC decoder

Since then it just errors out because it's too small, as it
wants the flac headers as codec data if there is codec data.

https://bugzilla.gnome.org/show_bug.cgi?id=589361

ext/ffmpeg/gstffmpegcodecmap.c

@@ -2387,7 +2387,8 @@ gst_ffmpeg_caps_with_codecid (enum CodecID codec_id,
     }
 
     GST_DEBUG ("have codec data of size %d", size);
-  } else if (context->extradata == NULL && codec_id != CODEC_ID_AAC_LATM) {
+  } else if (context->extradata == NULL && codec_id != CODEC_ID_AAC_LATM &&
+      codec_id != CODEC_ID_FLAC) {
     /* no extradata, alloc dummy with 0 sized, some codecs insist on reading
      * extradata anyway which makes then segfault. */
     context->extradata =