fftools/ffplay: Check return of swr_alloc_set_opts2()

This probably makes no difference but its more correct

Fixes: CID1503080 Unchecked return value

Sponsored-by: Sovereign Tech Fund
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit f44f441555)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

fftools/ffplay.c

@@ -2353,12 +2353,13 @@ static int audio_decode_frame(VideoState *is)
         av_channel_layout_compare(&af->frame->ch_layout, &is->audio_src.ch_layout) ||
         af->frame->sample_rate   != is->audio_src.freq           ||
         (wanted_nb_samples       != af->frame->nb_samples && !is->swr_ctx)) {
+        int ret;
         swr_free(&is->swr_ctx);
-        swr_alloc_set_opts2(&is->swr_ctx,
+        ret = swr_alloc_set_opts2(&is->swr_ctx,
                             &is->audio_tgt.ch_layout, is->audio_tgt.fmt, is->audio_tgt.freq,
                             &af->frame->ch_layout, af->frame->format, af->frame->sample_rate,
                             0, NULL);
-        if (!is->swr_ctx || swr_init(is->swr_ctx) < 0) {
+        if (ret < 0 || swr_init(is->swr_ctx) < 0) {
             av_log(NULL, AV_LOG_ERROR,
                    "Cannot create sample rate converter for conversion of %d Hz %s %d channels to %d Hz %s %d channels!\n",
                     af->frame->sample_rate, av_get_sample_fmt_name(af->frame->format), af->frame->ch_layout.nb_channels,