ra144enc: reject unsupported sample rates

libavcodec/ra144enc.c

@@ -564,5 +564,6 @@ AVCodec ff_ra_144_encoder = {
     .capabilities   = CODEC_CAP_DELAY | CODEC_CAP_SMALL_LAST_FRAME,
     .sample_fmts    = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16,
                                                      AV_SAMPLE_FMT_NONE },
+    .supported_samplerates = (const int[]){ 8000, 0 },
     .long_name      = NULL_IF_CONFIG_SMALL("RealAudio 1.0 (14.4K)"),
 };