No blowing up, show error instead

Author: shana

src/GitHub.App/Resources.Designer.cs

@@ -153,6 +153,9 @@
   <data name="PublishToTitle" xml:space="preserve">
     <value>Publish repository to {0}</value>
   </data>
+  <data name="RepositoryCloneFailedNoSelectedRepo" xml:space="preserve">
+    <value>No selected repository.</value>
+  </data>
   <data name="RepositoryCreationFailedAlreadyExists" xml:space="preserve">
     <value>Repository '{0}/{1}' already exists.</value>
   </data>

src/GitHub.App/Resources.resx

@@ -120,6 +120,11 @@ IObservable<Unit> OnCloneRepository(object state)
             {
                 var repository = SelectedRepository;
                 Debug.Assert(repository != null, "Should not be able to attempt to clone a repo when it's null");
+                if (repository == null)
+                {
+                    notificationService.ShowError(Resources.RepositoryCloneFailedNoSelectedRepo);
+                    return Observable.Return(Unit.Default);
+                }
                 // The following is a noop if the directory already exists.
                 operatingSystem.Directory.CreateDirectory(BaseRepositoryPath);
                 return cloneService.CloneRepository(repository.CloneUrl, repository.Name, BaseRepositoryPath);