Fix cppcheck reported issues (#333)

Fixes: https://github.com/microsoft/PowerToys/issues/266

src/runner/general_settings.cpp

@@ -73,7 +73,7 @@ void start_initial_powertoys() {
     }
     only_enable_some_powertoys = true;
   }
-  catch (std::exception ex) {
+  catch (std::exception&) {
     // Couldn't read the general settings correctly.
     // Load all powertoys.
     only_enable_some_powertoys = false;

src/runner/main.cpp

@@ -71,7 +71,7 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine
     Trace::EventLaunch();
 
     result = run_message_loop();
-  } catch (std::runtime_error err) {
+  } catch (std::runtime_error& err) {
     std::string err_what = err.what();
     MessageBoxW(NULL, std::wstring(err_what.begin(),err_what.end()).c_str(), L"Error", MB_OK | MB_ICONERROR);
     result = -1;

src/runner/powertoy_module.h

@@ -10,7 +10,7 @@
 class PowertoyModule;
 
 struct PowertoyModuleDeleter {
-  void operator()(PowertoyModuleIface* module) {
+  void operator()(PowertoyModuleIface* module) const {
     if (module) {
       powertoys_events().unregister_receiver(module);
       module->disable();
@@ -21,7 +21,7 @@ struct PowertoyModuleDeleter {
 
 struct PowertoyModuleDLLDeleter {
   using pointer = HMODULE;
-  void operator()(HMODULE  handle) {
+  void operator()(HMODULE  handle) const {
     FreeLibrary(handle);
   }
 };

src/runner/settings_window.cpp

@@ -23,7 +23,7 @@ json::value get_power_toys_settings() {
       json::value powertoys_config = json::value::parse(powertoy.get_config());
       result.as_object()[name] = powertoys_config;
     }
-    catch (json::json_exception ex) {
+    catch (json::json_exception&) {
       //Malformed JSON.
     }
   }