Bug fixed - Section Rendering error.

modules/docs/src/Volo.Docs.Web/Pages/Documents/Project/Index.cshtml.cs

@@ -542,6 +542,10 @@ namespace Volo.Docs.Pages.Documents.Project
 
                 Document.Content = await _documentSectionRenderer.RenderAsync(Document.Content, UserPreferences, partialTemplates);
             }
+            else
+            {
+                DocumentNavigationsDto = new DocumentNavigationsDto();
+            }
 
             var converter = _documentToHtmlConverterFactory.Create(Document.Format ?? Project.Format);
             var content = converter.Convert(Project, Document, GetSpecificVersionOrLatest(), LanguageCode, ProjectName);