Maintaining filter after postback, and fixing pager text with no results

--HG--
branch : dev
extra : transplant_source : %9D%83U%F6%AE%DCpT%D1%10%60%E3%5D%3D%89n%C2%60Qa

src/Orchard.Web/Modules/Orchard.Users/Controllers/AdminController.cs

@@ -133,7 +133,7 @@ namespace Orchard.Users.Controllers {
                     break;
             }
 
-            return RedirectToAction("Index");
+            return Index(viewModel.Options, new PagerParameters());
         }
 
         public ActionResult Create() {

src/Orchard.Web/Themes/TheAdmin/Views/Pager.cshtml

@@ -26,7 +26,11 @@
     Model.Classes.Add("group");
     var tag = Tag(Model, "ul");
 }
+
+@if (Model.TotalItemCount > 1) {
 	<span class="page-results">@T("Showing items {0} - {1} of {2}", (Model.Page-1)*(int)Model.PageSize + 1, Math.Min(Model.TotalItemCount, (Model.Page)*(int)Model.PageSize), Model.TotalItemCount)</span>
+}
+
 @if (totalPageCount > 1) {
     @tag.StartElement
     // first