Fix a warning: 'ex' unreferenced local variable

[fengga]

This is a

• Bugfix

I have

• Run the tests

After I updated easylogging from v9.96.7 to v9.97.0, this code:
catch(std::exception & ex){
// Extremely low memory situation; don't let exception be unhandled.
}
will generate a warning:
warning C4101: 'ex': unreferenced local variable
and our build will fail.

[simoc]

I would also like this Pull Request included in the next version of Easylogging++.

I have the same problem compiling with Visual Studio 2019 and this Pull Request solves the problem.

A simple test program using the master version of Easylogging++ demonstrates the problem:

C:\Git_Repos\easyloggingpp\src>cl /EHsc /W4 test783.cpp easylogging++.cc
Microsoft (R) C/C++ Optimizing Compiler Version 19.27.29112 for x86
Copyright (C) Microsoft Corporation.  All rights reserved.

test783.cpp
easylogging++.cc
easylogging++.cc(2657): warning C4101: 'ex': unreferenced local variable
Generating Code...
Microsoft (R) Incremental Linker Version 14.27.29112.0
Copyright (C) Microsoft Corporation.  All rights reserved.

/out:test783.exe
test783.obj
easylogging++.obj

[simoc]

@yanchoyanev are you able to merge this Pull Request to master?

[DominionSoftware]

Hi
please merge this to master