Fix: Make layout key nullable, default to application layout

modules/cms-kit/src/Volo.CmsKit.Admin.Application.Contracts/Volo/CmsKit/Admin/Pages/CreatePageInputDto.cs

@@ -17,7 +17,6 @@ public class CreatePageInputDto: ExtensibleObject
     [DynamicMaxLength(typeof(PageConsts), nameof(PageConsts.MaxSlugLength))]
     public string Slug { get; set; }
 
-    [Required]
     [DynamicMaxLength(typeof(PageConsts), nameof(PageConsts.MaxLayoutNameLength))]
     public string LayoutName { get; set; }
 

modules/cms-kit/src/Volo.CmsKit.Admin.Application.Contracts/Volo/CmsKit/Admin/Pages/UpdatePageInputDto.cs

@@ -18,7 +18,6 @@ public class UpdatePageInputDto : ExtensibleObject, IHasConcurrencyStamp
     [DynamicMaxLength(typeof(PageConsts), nameof(PageConsts.MaxSlugLength))]
     public string Slug { get; set; }
 
-    [Required]
     [DynamicMaxLength(typeof(PageConsts), nameof(PageConsts.MaxLayoutNameLength))]
     public string LayoutName { get; set; }
 

modules/cms-kit/src/Volo.CmsKit.Domain/Volo/CmsKit/Pages/Page.cs

@@ -78,7 +78,7 @@ public class Page : FullAuditedAggregateRoot<Guid>, IMultiTenant, IHasEntityVers
 
     public virtual void SetLayoutName(string layoutName) 
     {
-        LayoutName = Check.NotNullOrEmpty(layoutName, nameof(layoutName), PageConsts.MaxLayoutNameLength); 
+        LayoutName = Check.Length(layoutName, nameof(layoutName), PageConsts.MaxLayoutNameLength); 
     }
 
     internal void SetIsHomePage(bool isHomePage)

modules/cms-kit/src/Volo.CmsKit.Public.Web/Pages/CmsKit/Shared/Layouts/LayoutExtensions.cs

@@ -15,8 +15,8 @@ public static class LayoutExtensions
 
     public static string GetLayoutByKey(this ITheme theme, string layoutKey)
     {
-        return LayoutFunctions.TryGetValue(layoutKey, out var layoutFunc)
-            ? layoutFunc(theme)
-            : theme.GetApplicationLayout(); // Application layout is the default
+        return !string.IsNullOrWhiteSpace(layoutKey) && LayoutFunctions.TryGetValue(layoutKey, out var layoutFunc)
+           ? layoutFunc(theme)
+           : theme.GetApplicationLayout(); // Application layout is the default
     }
 }