ffplay: avoid useless NULL checks in swr_free()

swr_free() already checks for nullness, no need to add the check in
calling code.

ffplay.c

@@ -1963,7 +1963,6 @@ static int audio_decode_frame(VideoState *is, double *pts_ptr)
                 dec_channel_layout != is->audio_src.channel_layout ||
                 dec->sample_rate != is->audio_src.freq ||
                 (wanted_nb_samples != is->frame->nb_samples && !is->swr_ctx)) {
-                if (is->swr_ctx)
                 swr_free(&is->swr_ctx);
                 is->swr_ctx = swr_alloc_set_opts(NULL,
                                                  is->audio_tgt.channel_layout, is->audio_tgt.fmt, is->audio_tgt.freq,
@@ -2268,7 +2267,6 @@ static void stream_component_close(VideoState *is, int stream_index)
 
         packet_queue_flush(&is->audioq);
         av_free_packet(&is->audio_pkt);
-        if (is->swr_ctx)
         swr_free(&is->swr_ctx);
         av_freep(&is->audio_buf1);
         is->audio_buf = NULL;