[#11] Tests: Add MemberServiceTest

Elwig/App.xaml.cs

@@ -205,6 +205,7 @@ namespace Elwig {
         }
 
         public static void HintContextChange() {
+            if (CurrentApp == null) return;
             var ch = CurrentLastWrite;
             if (ch > CurrentApp.LastChanged)
                 CurrentApp.LastChanged = ch;