OPFS Hangs when using firefox

Please include the following in your bug report:

**Version of emscripten/emsdk:**
emcc -v
emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 4.0.9 (e93c648a75ee38bb6e021c4c16fd18cf8f9896e9)
clang version 21.0.0git (https:/github.com/llvm/llvm-project 2f05451198e2f222ec66cec4892ada0509519290)
Target: wasm32-unknown-emscripten
Thread model: posix

**Failing command line in full:**
emcc -s WASMFS -s PROXY_TO_PTHREAD=1 -s PTHREAD_POOL_SIZE=16 -pthread -o test.html test/wasmfs/wasmfs_opfs.c
emrun --browser=firefox test.html

The test runs, but if you reload the page a few times, it hangs.