Check the null value of UserAgent

src/main/scala/app/ControllerBase.scala

@@ -146,9 +146,11 @@ case class Context(settings: SystemSettingsService.SystemSettings, loginAccount:
   val baseUrl = settings.baseUrl(request)
   val host = new java.net.URL(baseUrl).getHost
   val platform = request.getHeader("User-Agent") match {
+    case null => null
     case agent if agent.contains("Mac") => "mac"
     case agent if agent.contains("Linux") => "linux"
     case agent if agent.contains("Win") => "windows"
+    case _ => null
   }
 
   /**

src/main/twirl/menu.scala.html

@@ -84,7 +84,7 @@
         </div>
       }
       @id.map { id =>
-        @if(context.platform != "linux"){
+        @if(context.platform != "linux" || context.platform != null){
         <div style="margin-top: 10px;">
           <a href="@repository.httpOpenRepoUrl(context.platform)" id="repository-clone-url" class="btn btn-small" style="width: 147px;"><i class="icon-download-alt"></i>Clone in Desktop</a>
         </div>