Hide language switch menu if the app has only one language.

Resolve #2204

framework/src/Volo.Abp.AspNetCore.Mvc.UI.Theme.Basic/Themes/Basic/Components/Toolbar/LanguageSwitch/Default.cshtml

@@ -1,14 +1,18 @@
-@using Volo.Abp.AspNetCore.Mvc.UI.Theme.Basic.Themes.Basic.Components.Toolbar.LanguageSwitch
+@using System.Linq
+@using Volo.Abp.AspNetCore.Mvc.UI.Theme.Basic.Themes.Basic.Components.Toolbar.LanguageSwitch
 @model LanguageSwitchViewComponentModel
-<div class="dropdown">
-    <a class="nav-link dropdown-toggle" href="#" role="button" id="dropdownMenuLink" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
-        @Model.CurrentLanguage.DisplayName
-    </a>
+@if (Model.OtherLanguages.Any())
+{
+    <div class="dropdown">
+        <a class="nav-link dropdown-toggle" href="#" role="button" id="dropdownMenuLink" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
+            @Model.CurrentLanguage.DisplayName
+        </a>
 
-    <div class="dropdown-menu dropdown-menu-right border-0 shadow-sm" aria-labelledby="dropdownMenuLink">
-        @foreach (var language in Model.OtherLanguages)
-        {
-            <a class="dropdown-item" href="/Abp/Languages/Switch?culture=@(language.CultureName)&uiCulture=@(language.UiCultureName)&returnUrl=@Context.Request.Path">@language.DisplayName</a>
-        }
-    </div>
-</div>
+        <div class="dropdown-menu dropdown-menu-right border-0 shadow-sm" aria-labelledby="dropdownMenuLink">
+            @foreach (var language in Model.OtherLanguages)
+            {
+                <a class="dropdown-item" href="/Abp/Languages/Switch?culture=@(language.CultureName)&uiCulture=@(language.UiCultureName)&returnUrl=@Context.Request.Path">@language.DisplayName</a>
+            }
+        </div>
+    </div> 
+}