fix(theme): null/whitespace-safe NavRailSection slug + edge tests

ZB.MOM.WW.Theme/src/ZB.MOM.WW.Theme/Components/NavRailSection.razor

@@ -31,8 +31,9 @@
 
     private string ResolvedKey => string.IsNullOrWhiteSpace(Key) ? Slug(Title) : Key!;
 
-    private static string Slug(string s)
+    private static string Slug(string? s)
     {
+        if (string.IsNullOrWhiteSpace(s)) return string.Empty;
         var chars = s.Trim().ToLowerInvariant()
             .Select(c => char.IsLetterOrDigit(c) ? c : '-').ToArray();
         return string.Join('-', new string(chars).Split('-', StringSplitOptions.RemoveEmptyEntries));

ZB.MOM.WW.Theme/tests/ZB.MOM.WW.Theme.Tests/NavRailTests.cs

@@ -73,4 +73,22 @@ public class NavRailTests : TestContext
             .AddChildContent("<a class='rail-link'>X</a>"));
         Assert.Equal("nav", cut.Find("details.rail-section").GetAttribute("data-nav-key"));
     }
+
+    [Fact]
+    public void NavRailSection_whitespace_only_title_yields_empty_data_nav_key()
+    {
+        var cut = RenderComponent<NavRailSection>(p => p
+            .Add(x => x.Title, "   ")
+            .AddChildContent("<a class='rail-link'>X</a>"));
+        Assert.Equal("", cut.Find("details.rail-section").GetAttribute("data-nav-key"));
+    }
+
+    [Fact]
+    public void NavRailSection_slug_preserves_unicode_letters()
+    {
+        var cut = RenderComponent<NavRailSection>(p => p
+            .Add(x => x.Title, "Café")
+            .AddChildContent("<a class='rail-link'>X</a>"));
+        Assert.Equal("café", cut.Find("details.rail-section").GetAttribute("data-nav-key"));
+    }
 }