Update Index.cshtml.cs

https://github.com/abpframework/abp/issues/1217

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

@@ -148,8 +148,7 @@ namespace Volo.Docs.Pages.Documents.Project
 
         private IActionResult ReloadPageWithCulture()
         {
-            var languageCodeWithSlashAtTheEnd = string.IsNullOrWhiteSpace(LanguageCode) ? "" : LanguageCode + "/";
+            var returnUrl = "/" + DocumentsUrlPrefix + LanguageCode + "/" + ProjectName + "/" + Version + "/" +
-            var returnUrl = "/" + DocumentsUrlPrefix + languageCodeWithSlashAtTheEnd + ProjectName + "/" + Version + "/" +
                             DocumentName;
 
             return Redirect("/Abp/Languages/Switch?culture=" + LanguageCode + "&uiCulture=" + LanguageCode + "&returnUrl=" + returnUrl);