Mandoline: ConnectToApplication and ConnectToService should fail gracefully

mojo/application/public/cpp/lib/application_impl.cc

Index: mojo/application/public/cpp/lib/application_impl.cc
diff --git a/mojo/application/public/cpp/lib/application_impl.cc b/mojo/application/public/cpp/lib/application_impl.cc
index 33023c68057d1689e7580fd55981de77265acf79..f1c6e42c6015935f9724c90519cf9858463e8289 100644
--- a/mojo/application/public/cpp/lib/application_impl.cc
+++ b/mojo/application/public/cpp/lib/application_impl.cc
@@ -65,7 +65,8 @@ ApplicationImpl::~ApplicationImpl() {
 
 ApplicationConnection* ApplicationImpl::ConnectToApplication(
     mojo::URLRequestPtr request) {
-  MOJO_CHECK(shell_);
+  if (!shell_)
+    return nullptr;
   ServiceProviderPtr local_services;
   InterfaceRequest<ServiceProvider> local_request = GetProxy(&local_services);
   ServiceProviderPtr remote_services;