avcodec/dvbsubdec: error out on unsupported coding methods

libavcodec/dvbsubdec.c

@@ -1034,10 +1034,13 @@ static int dvbsub_parse_object_segment(AVCodecContext *avctx,
         }
     } else if (coding_method == 1) {
         avpriv_report_missing_feature(avctx, "coded as a string of characters");
+        return AVERROR_PATCHWELCOME;
     } else if (coding_method == 2) {
         avpriv_report_missing_feature(avctx, "progressive coding of pixels");
+        return AVERROR_PATCHWELCOME;
     } else {
         av_log(avctx, AV_LOG_ERROR, "Unknown object coding %d\n", coding_method);
+        return AVERROR_INVALIDDATA;
     }
 
     return 0;