Ava UI: Fix locale crash (#6385)

* Fix locale crash

* Apply suggestions from code review

---------

Co-authored-by: Ac_K <Acoustik666@gmail.com>

src/Ryujinx/Common/Locale/LocaleManager.cs

@@ -30,28 +30,22 @@ namespace Ryujinx.Ava.Common.Locale
             Load();
         }
 
-        public void Load()
+        private void Load()
         {
-            // Load the system Language Code.
-            string localeLanguageCode = CultureInfo.CurrentCulture.Name.Replace('-', '_');
+            var localeLanguageCode = !string.IsNullOrEmpty(ConfigurationState.Instance.UI.LanguageCode.Value) ?
+                ConfigurationState.Instance.UI.LanguageCode.Value : CultureInfo.CurrentCulture.Name.Replace('-', '_');
 
-            // If the view is loaded with the UI Previewer detached, then override it with the saved one or default.
+            // Load en_US as default, if the target language translation is missing or incomplete.
+            LoadDefaultLanguage();
+            LoadLanguage(localeLanguageCode);
+
+            // Save whatever we ended up with.
             if (Program.PreviewerDetached)
             {
-                if (!string.IsNullOrEmpty(ConfigurationState.Instance.UI.LanguageCode.Value))
-                {
-                    localeLanguageCode = ConfigurationState.Instance.UI.LanguageCode.Value;
-                }
-                else
-                {
-                    localeLanguageCode = DefaultLanguageCode;
-                }
-            }
+                ConfigurationState.Instance.UI.LanguageCode.Value = _localeLanguageCode;
 
-            // Load en_US as default, if the target language translation is incomplete.
-            LoadDefaultLanguage();
-
-            LoadLanguage(localeLanguageCode);
+                ConfigurationState.Instance.ToFileFormat().SaveConfig(Program.ConfigurationPath);
+            }
         }
 
         public string this[LocaleKeys key]
@@ -126,24 +120,42 @@ namespace Ryujinx.Ava.Common.Locale
 
         private void LoadDefaultLanguage()
         {
-            _localeDefaultStrings = LoadJsonLanguage();
+            _localeDefaultStrings = LoadJsonLanguage(DefaultLanguageCode);
         }
 
         public void LoadLanguage(string languageCode)
         {
-            foreach (var item in LoadJsonLanguage(languageCode))
+            var locale = LoadJsonLanguage(languageCode);
+
+            if (locale == null)
+            {
+                _localeLanguageCode = DefaultLanguageCode;
+                locale = _localeDefaultStrings;
+            }
+            else
+            {
+                _localeLanguageCode = languageCode;
+            }
+
+            foreach (var item in locale)
             {
                 this[item.Key] = item.Value;
             }
 
-            _localeLanguageCode = languageCode;
             LocaleChanged?.Invoke();
         }
 
-        private static Dictionary<LocaleKeys, string> LoadJsonLanguage(string languageCode = DefaultLanguageCode)
+        private static Dictionary<LocaleKeys, string> LoadJsonLanguage(string languageCode)
         {
             var localeStrings = new Dictionary<LocaleKeys, string>();
             string languageJson = EmbeddedResources.ReadAllText($"Ryujinx/Assets/Locales/{languageCode}.json");
+
+            if (languageJson == null)
+            {
+                // We were unable to find file for that language code.
+                return null;
+            }
+
             var strings = JsonHelper.Deserialize(languageJson, CommonJsonContext.Default.StringDictionary);
 
             foreach (var item in strings)