Add missing break statement in dvbsubdec.c

Mea culpa - those are my mods to the dvb subtitle decoder.
(cherry picked from commit af0f68e)

mythtv/external/FFmpeg/libavcodec/dvbsubdec.c

@@ -1481,6 +1481,7 @@ static int dvbsub_decode(AVCodecContext *avctx,
                 break;
             case DVBSUB_DISPLAYDEFINITION_SEGMENT:
                 dvbsub_parse_display_definition_segment(avctx, p, segment_length);
+                break;
             case DVBSUB_DISPLAY_SEGMENT:
                 *data_size = dvbsub_display_end_segment(avctx, p, segment_length, sub);
                 break;