Fix provider setter

Author: walterlv

src/dotnetCampus.Localizations.Analyzer/Assets/Templates/ImmutableLocalization.g.cs

@@ -118,6 +118,7 @@ private static ILocalizedStringProvider GetOrCreateLocalizedStringProvider(strin
             return provider;
         }
         var fallbackTag = global::dotnetCampus.Localizations.Helpers.LocalizationHelper.MatchWithFallback(languageTag, SupportedLanguageTags);
+        provider = fallbackTag is null ? null : CreateLocalizedStringProviderCore(fallbackTag);
         if (provider is not null)
         {
             return provider;

src/dotnetCampus.Localizations.Analyzer/Assets/Templates/NotifiableLocalization.g.cs

@@ -91,6 +91,7 @@ private static ILocalizedStringProvider CreateLocalizedStringProvider(string lan
             return provider;
         }
         var fallbackTag = global::dotnetCampus.Localizations.Helpers.LocalizationHelper.MatchWithFallback(languageTag, SupportedLanguageTags);
+        provider = fallbackTag is null ? null : CreateLocalizedStringProviderCore(fallbackTag);
         if (provider is not null)
         {
             return provider;