FEXConfig: "Most likely this is a multi-threaded client and XInitThreads has not been called"
I tried to run FEXConfig to configure FEX, but I got this
```
[xcb] Unknown sequence number while processing queue
[xcb] Most likely this is a multi-threaded client and XInitThreads has not been called
[xcb] Aborting, sorry about that.
FEXConfig: xcb_io.c:269: poll_for_event: Assertion `!xcb_xlib_threads_sequence_lost' failed.
Aborted (core dumped)
```
I had a black screen flash before dumping this.