No compiler was found.In order to use a C++ template, you must first install Xcode.

Please help! I cannot use my mac for UE4 development anymore.
When I tried creating a new project with C++, it occur as in the attached image. I also cannot compile C++ code of existing project.
I have been using CLion with plugins

What happened :
I have been working with C++ for a few days. When one day I wrote a code (access a null variable) it made the UE4 editor crashed down. When I opened it up, the compile button disappear. Then I also cannot create new project with C++ template.

My spec :
Macbook Pro 2017 Sierra (at the time it happened) then upgraded to High Sierra after that
UE 4.18 when it happened then tried both 4.17 and 4.19
use CLion and plugin from here GitHub - dotBunny/CLionSourceCodeAccess: A CLion Plugin for Unreal Engine

What I have tried :
I tried uninstalling UE4 and Epic launcher.
I tried uninstalling and reinstalling Xcode.
I tried upgrading to High Sierra
I tried installing 4.18.3
I tried installing 4.19.0 preview 3
deleted Saved/Intermediate/Binaries

None of them help me.

Thank you very much for any help.
Gap