ffplay: more robust condition variable creation

SDL_CreateCond can fail:
https://wiki.libsdl.org/SDL_CreateCond.
This patch makes creation more robust in one instance.
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
Signed-off-by: Marton Balint <cus@passwd.hu>

ffplay.c

@@ -3168,7 +3168,10 @@ static VideoState *stream_open(const char *filename, AVInputFormat *iformat)
         packet_queue_init(&is->subtitleq) < 0)
         goto fail;
 
-    is->continue_read_thread = SDL_CreateCond();
+    if (!(is->continue_read_thread = SDL_CreateCond())) {
+        av_log(NULL, AV_LOG_FATAL, "SDL_CreateCond(): %s\n", SDL_GetError());
+        goto fail;
+    }
 
     init_clock(&is->vidclk, &is->videoq.serial);
     init_clock(&is->audclk, &is->audioq.serial);