`createWalletFull`, `importOutputs` and `exportKeyImages` cannot function correctly when a deposit is made to a subaddress with large index
Hi there,

I use the view-only wallet plus offline wallet mechanism to sign keyImages.

![image](https://user-images.githubusercontent.com/81351621/182318538-f29ccd4a-e03f-4984-8feb-a65649debc75.png)

I use `try catch`s to locate the error to be throw by the last line above: `TypeError: (intermediate value) is not iterable`. I check the `monero-javascript` repo and doubt if it is thrown by the line in the red box below:

<img width="1057" alt="Screen Shot 2022-08-02 at 15 38 11" src="https://user-images.githubusercontent.com/81351621/182319228-d761cb71-af67-4735-8556-7311319376a1.png">

..., because a `null` value is not iterable.

From my understanding `that._module.export_key_images(that._cppAddress, all, callback);` calls the wasm function which was translated from c++. Is there a way to debug the wasm code? Below is an excerpt from `monero_wasm_bridge.cpp`:

<img width="878" alt="Screen Shot 2022-08-02 at 15 42 04" src="https://user-images.githubusercontent.com/81351621/182319937-235e49ac-6b03-4bd4-85c5-c316648270d3.png">

I suppose something went wrong at this line `doc.AddMember("keyImages", monero_utils::to_rapidjson_val(doc.GetAllocator(), key_images), doc.GetAllocator());` Somehow the doc object cannot locate memory or something, so the later half returns `null`. Do you know what causes the original error when `exportKeyImages`, or what could cause `doc.AddMember` to return a bug?