[Bug] Crashes at RemoteConfigResponse related to FlatBufferBuilder

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### [REQUIRED] Please fill in the following fields:

* Pre-built SDK from the [website](https://firebase.google.com/download/cpp) or open-source from this repo: 10.3.0
* Firebase C++ SDK version: 10.3.0
* Main Firebase Components in concern: remote_config
* Other Firebase Components in use: auth
* Platform you are using the C++ SDK on: windows
* Platform you are targeting: windows

### [REQUIRED] Please describe the question here:
hi, I found some crash on my customer's PC,
from the minidump, the crash is like this:
the rdx is zero

and the correspond code is
the rbx+68h get the builder_
the rax+170h use the builder_ get the buffer pointer,
the crash reason is GetRoot function will try use the buffer pointer from builder_,
but if the buffer pointer is null, it will crash,
so I think it should do some protect like this:

FlatBufferBuilder、builder_、GetRoot が関係する RemoteConfigResponse のコードパスから始め、Windows SDK 10.3.0 のパスで null バッファーがどのように発生し得るかを調査してください。その状態で意図されている動作を確認し、報告された minidump パスでクラッシュが発生しなくなったことを検証してください。

索引モデルが issue の本文から書いたものです。