Bugfix: Reference to master language changed after removing one language.

src/Squidex.Domain.Apps.Core.Model/Apps/LanguagesConfig.cs

@@ -121,8 +121,7 @@ namespace Squidex.Domain.Apps.Core.Apps
                     .ToImmutableDictionary(x => x.Language);
 
             var newMaster =
-                Master.Language != language ?
+                newLanguages.Values.FirstOrDefault(x => x.Language == Master.Language) ??
-                Master :
                 newLanguages.Values.FirstOrDefault();
 
             return new LanguagesConfig(newLanguages, newMaster);

tests/Squidex.Domain.Apps.Core.Tests/Model/Apps/LanguagesConfigTests.cs

@@ -139,6 +139,8 @@ namespace Squidex.Domain.Apps.Core.Model.Apps
             var config_0 = LanguagesConfig.Build(Language.DE, Language.IT, Language.RU);
             var config_1 = config_0.Remove(Language.IT);
 
+            Assert.Same(config_1.Master, config_1.OfType<LanguageConfig>().FirstOrDefault(x => x.Language == Language.DE));
+
             config_1.ToList().ShouldBeEquivalentTo(
                 new List<LanguageConfig>
                 {