chore: Fix getting value type keys from IKeyValueStorage

src/Uno.Extensions.Storage.UI/KeyValueStorage/BaseKeyValueStorageWithCaching.cs

@@ -33,7 +33,7 @@ public async ValueTask ClearAsync(string key, CancellationToken ct)
 			if (!settings.DisableInMemoryCache)
 			{
 				var val = await InMemoryStorage.GetAsync<TValue>(key, ct);
-				if (val is not null)
+				if (val != default(TValue))
 				{
 					return val;
 				}