Crash in tuningfork::HttpRequest::Send

Hi, we're using Andriod Performance Tuner with Unity, and saw the following crash shown in Google Play Console:
```
backtrace:
#00 pc 0x0000000000083860 /apex/com.android.runtime/lib64/bionic/libc.so (abort+176)
#01 pc 0x00000000004bb244 /apex/com.android.runtime/lib64/libart.so (art::Runtime::Abort(char const*)+2172)
#02 pc 0x000000000000c650 /system/lib64/libbase.so (android::base::LogMessage::~LogMessage()+608)
#03 pc 0x000000000037923c /apex/com.android.runtime/lib64/libart.so (art::JavaVMExt::JniAbort(char const*, char const*)+1604)
#04 pc 0x000000000038bb20 /apex/com.android.runtime/lib64/libart.so (art::JNI::GetMethodID(_JNIEnv*, _jclass*, char const*, char const*)+1432)
#05 pc 0x0000000000053084 /data/app/com.xxx.yyy-sDyHGiOxpQyp72Hx_ZVqSQ==/lib/arm64/libunitytuningfork.so
#06 pc 0x00000000000220c8 /data/app/com.xxx.yyy-sDyHGiOxpQyp72Hx_ZVqSQ==/lib/arm64/libunitytuningfork.so
#07 pc 0x0000000000046f14 /data/app/com.xxx.yyy-sDyHGiOxpQyp72Hx_ZVqSQ==/lib/arm64/libunitytuningfork.so (tuningfork::HttpRequest::Send(std::__ndk1::basic_string, std::__ndk1::allocator > const&, std::__ndk1::basic_string, std::__ndk1::allocator > const&, int&, std::__ndk1::basic_string, std::__ndk1::allocator >&)+112)
#08 pc 0x000000000005290c /data/app/com.xxx.yyy-sDyHGiOxpQyp72Hx_ZVqSQ==/lib/arm64/libunitytuningfork.so (tuningfork::UltimateUploader::CheckUploadPending()+244)
#09 pc 0x0000000000052804 /data/app/com.xxx.yyy-sDyHGiOxpQyp72Hx_ZVqSQ==/lib/arm64/libunitytuningfork.so (tuningfork::UltimateUploader::DoWork()+8)
#10 pc 0x000000000003460c /data/app/com.xxx.yyy-sDyHGiOxpQyp72Hx_ZVqSQ==/lib/arm64/libunitytuningfork.so (tuningfork::Runnable::Run()+120)
#11 pc 0x00000000000347b8 /data/app/com.xxx.yyy-sDyHGiOxpQyp72Hx_ZVqSQ==/lib/arm64/libunitytuningfork.so
#12 pc 0x00000000000e55b4 /apex/com.android.runtime/lib64/bionic/libc.so (__pthread_start(void*)+36)
#13 pc 0x0000000000085458 /apex/com.android.runtime/lib64/bionic/libc.so (__start_thread+64)
```

Other information:
* Unity: 2020.3.30 with Addressables
* Android Performance Tuner: 1.5.2

Start at the tuningfork::HttpRequest::Send entry point identified in the crash stack, then review the surrounding upload path through UltimateUploader::CheckUploadPending. Reproduce with Unity 2020.3.30, Addressables, and Android Performance Tuner 1.5.2 if possible; done means the JNI-related crash no longer occurs during upload.

Written by the indexing model from the issue text.