pulse: fix race in TimeGet()

Cork state could change asynchronously without the PA lock.

modules/audio_output/pulse.c

@@ -441,16 +441,20 @@ static int TimeGet(audio_output_t *aout, mtime_t *restrict delay)
 {
     aout_sys_t *sys = aout->sys;
     pa_stream *s = sys->stream;
+    int ret = -1;
 
-    if (pa_stream_is_corked(s) > 0)
-        return -1; /* latency is irrelevant if corked */
-
+    pa_threaded_mainloop_lock(sys->mainloop);
+    if (pa_stream_is_corked(s) <= 0)
+    {   /* latency is relevant only if not corked */
         mtime_t delta = vlc_pa_get_latency(aout, sys->context, s);
-    if (delta == VLC_TS_INVALID)
-        return -1;
-
+        if (delta != VLC_TS_INVALID)
+        {
             *delay = delta;
-    return 0;
+            ret = 0;
+        }
+    }
+    pa_threaded_mainloop_unlock(sys->mainloop);
+    return ret;
 }
 
 /* Memory free callback. The block_t address is in front of the data. */