Config: Handle unknown system strings better

Currently, a simple typo in the system name will trigger an assert
message that complains about a "programming error". This is not
user friendly and misleading.

So this changes GetSystemFromName to return an std::optional, which
allows for callers to check whether the system exists and handle
failures better.

Source/Core/Common/Config/Config.cpp

@@ -101,15 +101,14 @@ const std::string& GetSystemName(System system)
   return system_to_name.at(system);
 }
 
-System GetSystemFromName(const std::string& name)
+std::optional<System> GetSystemFromName(const std::string& name)
 {
   const auto system = std::find_if(system_to_name.begin(), system_to_name.end(),
                                    [&name](const auto& entry) { return entry.second == name; });
   if (system != system_to_name.end())
     return system->first;
 
-  _assert_msg_(COMMON, false, "Programming error! Couldn't convert '%s' to system!", name.c_str());
+  return {};
-  return System::Main;
 }
 
 const std::string& GetLayerName(LayerType layer)

Source/Core/Common/Config/Config.h

@@ -7,6 +7,7 @@
 #include <functional>
 #include <map>
 #include <memory>
+#include <optional>
 #include <string>
 
 #include "Common/Config/ConfigInfo.h"
@@ -38,7 +39,7 @@ void Shutdown();
 void ClearCurrentRunLayer();
 
 const std::string& GetSystemName(System system);
-System GetSystemFromName(const std::string& system);
+std::optional<System> GetSystemFromName(const std::string& system);
 const std::string& GetLayerName(LayerType layer);
 LayerType GetActiveLayerForConfig(const ConfigLocation&);
 

Source/Core/Core/ConfigLoaders/GameConfigLoader.cpp

@@ -157,8 +157,9 @@ static ConfigLocation MapINIToRealLocation(const std::string& section, const std
     std::getline(buffer, config_section, '.');
     fail |= buffer.fail();
 
-    if (!fail)
+    const std::optional<Config::System> system = Config::GetSystemFromName(system_str);
-      return {Config::GetSystemFromName(system_str), config_section, key};
+    if (!fail && system)
+      return {*system, config_section, key};
 
     WARN_LOG(CORE, "Unknown game INI option in section %s: %s", section.c_str(), key.c_str());
     return {Config::System::Main, "", ""};

Source/Core/UICommon/CommandLineParse.cpp

@@ -3,6 +3,7 @@
 // Refer to the license.txt file included.
 
 #include <list>
+#include <optional>
 #include <sstream>
 #include <string>
 #include <tuple>
@@ -40,8 +41,12 @@ public:
       std::getline(buffer, section, '.');
       std::getline(buffer, key, '=');
       std::getline(buffer, value, '=');
-      Config::System system = Config::GetSystemFromName(system_str);
+      const std::optional<Config::System> system = Config::GetSystemFromName(system_str);
-      m_values.emplace_back(std::make_tuple(Config::ConfigLocation{system, section, key}, value));
+      if (system)
+      {
+        m_values.emplace_back(
+            std::make_tuple(Config::ConfigLocation{*system, section, key}, value));
+      }
     }
   }