[Build]Fix uninitialized variable error on VS 17.8 (#29860)

src/modules/EnvironmentVariables/EnvironmentVariablesModuleInterface/dllmain.cpp

@@ -53,7 +53,7 @@ private:
     //contains the non localized key of the powertoy
     std::wstring app_key;
 
-    HANDLE m_hProcess;
+    HANDLE m_hProcess = nullptr;
 
     HANDLE m_hShowEvent;