Fix 'duplicate setting' errors when running installation wizard

apps/launcher/maindialog.cpp

@@ -384,6 +384,9 @@ bool Launcher::MainDialog::setupGraphicsSettings()
     // remain consistent, and possibly be merged into a shared component.  At the very least
     // the filenames should be in the CfgMgr component.
 
+    // Ensure to clear previous settings in case we had already loaded settings.
+    mEngineSettings.clear();
+
     // Create the settings manager and load default settings file
     const std::string localDefault = (mCfgMgr.getLocalPath() / "settings-default.cfg").string();
     const std::string globalDefault = (mCfgMgr.getGlobalPath() / "settings-default.cfg").string();

components/settings/settings.cpp

@@ -353,6 +353,13 @@ private:
     int mLine;
 };
 
+void Manager::clear()
+{
+    mDefaultSettings.clear();
+    mUserSettings.clear();
+    mChangedSettings.clear();
+}
+
 void Manager::loadDefault(const std::string &file)
 {
     SettingsFileParser parser;

components/settings/settings.hpp

@@ -23,6 +23,9 @@ namespace Settings
         static CategorySettingVector mChangedSettings;
         ///< tracks all the settings that were changed since the last apply() call
 
+        void clear();
+        ///< clears all settings and default settings
+
         void loadDefault (const std::string& file);
         ///< load file as the default settings (can be overridden by user settings)