EMSCRIPTEN_FETCH_PERSIST_FILE doesn't seem to persist to IndexedDB

I'm trying to persist downloaded files with fetch and IndexedDB. This was working fine for a while, but it appears to have stopped working at some point, I'm not sure when. This is the code I am using:

```
emscripten_fetch_attr_t attr;
emscripten_fetch_attr_init(&attr);
strcpy(attr.requestMethod, "GET");
attr.onsuccess = downloadSucceeded;
attr.onerror = downloadFailed;
attr.userData = req;
attr.attributes = EMSCRIPTEN_FETCH_LOAD_TO_MEMORY | EMSCRIPTEN_FETCH_PERSIST_FILE;

emscripten_fetch(&attr, req->ctx->uri.c_str());
```

`emscripten_filesystem` appears in the IndexedDB section of chrome, but no files appear in there. Any help would be appreciated!

Please include the following in your bug report:

**Version of emscripten/emsdk:**
```
emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.3 (c06156773675b2cb437e41459c12d44bd9a8f235)
clang version 14.0.0 (https://github.com/llvm/llvm-project d8f929a567083a6b90264193f1e4476f6b77c5fe)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /emsdk/upstream/bin
```

**Full link command and output with `-v` appended:**
```
"/emsdk/node/14.18.2_64bit/bin/node" /emsdk/upstream/emscripten/src/compiler.js /tmp/tmpi6mhtfsl.json
"/emsdk/upstream/bin/wasm-ld" -o development/index.wasm obj/development_x86/game_app/MainApp.o obj/development_x86/game_app/main.o -Lbin/development_x86 -L/usr/lib32 bin/development_x86/libgame.a bin/development_x86/libengine.a bin/development_x86/libbase.a bin/development_x86/libcommon.a bin/development_x86/libgameplay.a bin/development_x86/libdraco.a bin/development_x86/libdetour.a bin/development_x86/libspdlog.a bin/development_x86/libphysx.a bin/development_x86/libbx.a bin/development_x86/libbimg.a bin/development_x86/libbgfx.a bin/development_x86/libNoesis.a bin/development_x86/libcryptopp.a bin/development_x86/libmodl.a -L/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten /emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten/crtbegin.o --whole-archive -lfetch-mt -lGL-mt-webgl2-full_es3 --no-whole-archive -lal -lhtml5 -lstubs -lnoexit -lc-mt -ldlmalloc-mt -lcompiler_rt-mt -lc++-mt -lc++abi-mt -lsockets-mt -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-cxx-exceptions -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr --allow-undefined-file=/tmp/tmptyhi3hq5.undefined --import-memory --shared-memory --export-if-defined=main --export-if-defined=resize_window --export-if-defined=set_max_download_count --export-if-defined=handle_connection --export-if-defined=_emscripten_thread_init --export-if-defined=_emscripten_thread_exit --export-if-defined=emscripten_tls_init --export-if-defined=emscripten_current_thread_process_queued_calls --export-if-defined=pthread_self --export-if-defined=__start_em_asm --export-if-defined=__stop_em_asm --export=stackSave --export=stackRestore --export=stackAlloc --export=__wasm_call_ctors --export=__errno_location --export=emscripten_dispatch_to_thread_ --export=_emscripten_main_thread_futex --export=_emscripten_thread_free_data --export=_emscripten_allow_main_runtime_queued_calls --export=emscripten_main_browser_thread_id --export=emscripten_main_thread_process_queued_calls --export=emscripten_run_in_main_runtime_thread_js --export=emscripten_stack_set_limits --export=emscripten_sync_run_in_main_thread_2 --export=emscripten_sync_run_in_main_thread_4 --export=memalign --export=malloc --export=free --export=__cxa_is_pointer_type --export=__cxa_can_catch --export=setThrew --export=__dl_seterr --export=ntohs --export=htons --export=strlen --export=saveSetjmp --export-table -z stack-size=5242880 --initial-memory=67108864 --entry=main --max-memory=2147483648 --global-base=1024
"/emsdk/upstream/bin/wasm-emscripten-finalize" --minimize-wasm-changes -g --dyncalls-i64 --dwarf development/index.wasm -o development/index.wasm --detect-features
"/emsdk/node/14.18.2_64bit/bin/node" /emsdk/upstream/emscripten/src/compiler.js /tmp/tmpyyt2k8sp.json
"/emsdk/upstream/bin/wasm-opt" --post-emscripten -O2 --low-memory-unused --zero-filled-memory --strip-producers development/index.wasm -o development/index.wasm -g --mvp-features --enable-threads --enable-mutable-globals --enable-bulk-memory --enable-sign-ext
"/emsdk/node/14.18.2_64bit/bin/node" /emsdk/upstream/emscripten/tools/acorn-optimizer.js /tmp/emscripten_temp_j6wwvmb6/index.js growableHeap
"/emsdk/node/14.18.2_64bit/bin/node" /emsdk/upstream/emscripten/tools/preprocessor.js /tmp/emscripten_temp_j6wwvmb6/settings.js worker.js --expandMacros
"/emsdk/node/14.18.2_64bit/bin/node" /emsdk/upstream/emscripten/tools/preprocessor.js /tmp/emscripten_temp_j6wwvmb6/settings.js index.html
```