Fix QVariant not recognizing convertable types

The QMetaType did not correctly recognize that bools and doubles were
convertable from QVariant.

The new method is more robust.

src/settings/settings_internal.h

@@ -75,11 +75,20 @@ void saveQtSetting( const SettingCategory category,
     getQSettings().endGroup();
 }
 
-[[nodiscard]] bool isValidQVariant( const QVariant v,
-                                    const QMetaType::Type type )
+template <typename Value>[[nodiscard]] bool isValidQVariant( const QVariant v )
 {
-    const auto savedSettingIsValid
-        = v.isValid() && !v.isNull() && ( v.userType() == type );
+    auto savedSettingIsValid = v.isValid() && !v.isNull();
+
+    if constexpr ( std::is_same<Value, std::string>::value )
+    {
+        // Special case for std::string because Qt refuses to recognize it
+        savedSettingIsValid = savedSettingIsValid && v.canConvert<QString>();
+    }
+    else
+    {
+        savedSettingIsValid = savedSettingIsValid && v.canConvert<Value>();
+    }
+
     if ( savedSettingIsValid )
     {
         return true;

src/settings/specific_setting_value.h

@@ -26,25 +26,7 @@ public:
         const auto v = getQtSetting( SettingValue::category(),
                                      SettingValue::qtInfo().settingName );
 
-        QMetaType::Type type;
-        if constexpr ( std::is_same<Value, bool>::value )
-        {
-            type = QMetaType::Bool;
-        }
-        else if constexpr ( std::is_same<Value, double>::value )
-        {
-            type = QMetaType::Double;
-        }
-        else if constexpr ( std::is_same<Value, std::string>::value )
-        {
-            type = QMetaType::QString;
-        }
-        else if constexpr ( std::is_same<Value, int>::value )
-        {
-            type = QMetaType::Int;
-        }
-
-        if ( isValidQVariant( v, type ) )
+        if ( isValidQVariant<Value>( v ) )
         {
             if constexpr ( std::is_same<Value, bool>::value )
             {