ios/videotoolbox: fix crash when create vtb session failed

ios/IJKMediaPlayer/IJKMediaPlayer/ijkmedia/ijkplayer/ios/pipeline/IJKVideoToolBox.m

@@ -1119,6 +1119,10 @@ VideoToolBoxContext* videotoolbox_create(FFPlayer* ffp, AVCodecContext* avctx)
     int ret = 0;
 
     VideoToolBoxContext *context_vtb = (VideoToolBoxContext *)mallocz(sizeof(VideoToolBoxContext));
+
+    context_vtb->sample_info_mutex = SDL_CreateMutex();
+    context_vtb->sample_info_cond  = SDL_CreateCond();
+
     if (!context_vtb) {
         goto fail;
     }
@@ -1146,9 +1150,6 @@ VideoToolBoxContext* videotoolbox_create(FFPlayer* ffp, AVCodecContext* avctx)
     context_vtb->m_sort_queue = 0;
     context_vtb->m_queue_depth = 0;
 
-    context_vtb->sample_info_mutex = SDL_CreateMutex();
-    context_vtb->sample_info_cond  = SDL_CreateCond();
-
     SDL_SpeedSamplerReset(&context_vtb->sampler);
     return context_vtb;