EMSCRIPTEN_FETCH_NO_DOWNLOAD still attempts http get

```
emscripten_fetch_attr_t attr;
emscripten_fetch_attr_init(&attr);
{
// what this does: fetch file from IndexedDB if exists
strcpy(attr.requestMethod, "GET");
attr.attributes =
EMSCRIPTEN_FETCH_LOAD_TO_MEMORY /* s.t. we get the actual bytes of data */ |
EMSCRIPTEN_FETCH_PERSIST_FILE /* from IndexedDB */ |
EMSCRIPTEN_FETCH_NO_DOWNLOAD /* prevent falling back to xhs get if not in IndexedDB */;

attr.userData = this;
attr.onsuccess = downloadSucceeded;
attr.onerror = downloadFailed;
}
```
Hi, I'm attempting the above, but it looks like this still attempts to fetch over the network if the file doesn't exist in IndexedDB