Fix language display for ISO 639-2-only codes (e.g. mul, und)

LoadCultures() in LocalizationManager skipped all iso6392.txt entries
without a two-letter ISO 639-1 code, dropping 302 of 496 languages
including mul (Multiple languages), und (Undetermined), mis (Uncoded
languages), zxx, and many real languages like Achinese, Akkadian, etc.
This caused FindLanguageInfo() to return null for these codes, which
meant:
- ExternalPathParser could not recognize them as valid language codes
  in subtitle filenames, so the Language field was never set
- DisplayTitle fell back to the raw code string (e.g. "Mul")

Fix by allowing entries without two-letter codes to be loaded with an
empty TwoLetterISOLanguageName. Also set LocalizedLanguage in
ProbeResultNormalizer for ffprobe-detected streams (the DB repository
path was already handled on master).

1 files changed, 20 insertions, 1 deletions

diff --git a/tests/Jellyfin.Server.Implementations.Tests/Localization/LocalizationManagerTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Localization/LocalizationManagerTests.cs
index e60522bf78..700ac5dced 100644
--- a/tests/Jellyfin.Server.Implementations.Tests/Localization/LocalizationManagerTests.cs
+++ b/tests/Jellyfin.Server.Implementations.Tests/Localization/LocalizationManagerTests.cs
@@ -41,7 +41,7 @@ namespace Jellyfin.Server.Implementations.Tests.Localization
             await localizationManager.LoadAll();
             var cultures = localizationManager.GetCultures().ToList();
 
-            Assert.Equal(194, cultures.Count);
+            Assert.Equal(496, cultures.Count);
 
             var germany = cultures.FirstOrDefault(x => x.TwoLetterISOLanguageName.Equals("de", StringComparison.Ordinal));
             Assert.NotNull(germany);
@@ -99,6 +99,25 @@ namespace Jellyfin.Server.Implementations.Tests.Localization
             Assert.Contains("ger", germany.ThreeLetterISOLanguageNames);
         }
 
+        [Theory]
+        [InlineData("mul", "Multiple languages")]
+        [InlineData("und", "Undetermined")]
+        [InlineData("mis", "Uncoded languages")]
+        [InlineData("zxx", "No linguistic content; Not applicable")]
+        public async Task FindLanguageInfo_ISO6392Only_Success(string code, string expectedDisplayName)
+        {
+            var localizationManager = Setup(new ServerConfiguration
+            {
+                UICulture = "en-US"
+            });
+            await localizationManager.LoadAll();
+
+            var culture = localizationManager.FindLanguageInfo(code);
+            Assert.NotNull(culture);
+            Assert.Equal(expectedDisplayName, culture.DisplayName);
+            Assert.Equal(code, culture.ThreeLetterISOLanguageName);
+        }
+
         [Fact]
         public async Task GetParentalRatings_Default_Success()
         {