Fix parsing localization cookie when the value is not present

Oqtane.Test/Oqtane.Client.Tests/LocalizationCookieTests.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Localization;
+using Xunit;
+
+namespace Oqtane.Oqtane.Client.Tests
+{
+    public class LocalizationCookieTests
+    {
+        [Theory]
+        [InlineData("c=ar|uic=ar", "ar")]
+        [InlineData("c=ar", null)]
+        [InlineData("", null)]
+        [InlineData(null, null)]
+        public void ParseCookie(string localizationCookie, string expectedCulture)
+        {
+            // Arrange
+            var localizationCookieValue = CookieRequestCultureProvider.ParseCookieValue(localizationCookie);
+
+            // Act
+            var culture = localizationCookieValue?.UICultures?[0].Value;
+
+            // Assert
+            Assert.Equal(expectedCulture, culture);
+        }
+    }
+}