examples/perf/io-perf fails with segmentation fault with io-uring:

examples/perf/io-perf fails with segmentation fault with io-uring:
```
(gdb) run
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: io-perf --disk-path /dev/nvme2n1p2 --disk_size 100000000000 --io_uring
2024/05/09 15:54:40.117604|INFO |th=0000000000000000|photon_io_perf.cpp:79|main:Specify disk /dev/nvme2n1p2 size 100000000000
2024/05/09 15:54:40.117801|INFO |th=00007FFFF782A200|iouring-wrapper.cpp:668|new_iouring:Init event engine: iouring [is_master=1]
2024/05/09 15:54:40.117813|INFO |th=00007FFFF782A200|iouring-wrapper.cpp:516|check_register_file_support:iouring: register_files is enabled

Program received signal SIGSEGV, Segmentation fault.
0x0000000000817826 in free ()
(gdb) bt
#0 0x0000000000817826 in free ()
#1 0x0000000000440a54 in photon::iouringEngine::init() ()
#2 0x000000000043f664 in photon::new_iouring(bool) ()
#3 0x00000000004229d5 in photon::init(unsigned long, unsigned long, photon::PhotonOptions const&) ()
#4 0x000000000041c40a in main ()
```

Reproduce the crash from examples/perf/io-perf using the shown --io_uring invocation and inspect photon_io_perf.cpp:79. Trace initialization through new_iouring() and iouringEngine::init() in iouring-wrapper.cpp, using the provided backtrace as the starting point. Done means the io-perf example no longer segfaults during io-uring startup.

Written by the indexing model from the issue text.