Clean up MojoShellConnection in render processes

mojo/shell/runner/host/out_of_process_native_runner.cc

Index: mojo/shell/runner/host/out_of_process_native_runner.cc
diff --git a/mojo/shell/runner/host/out_of_process_native_runner.cc b/mojo/shell/runner/host/out_of_process_native_runner.cc
index cea56bc53c9625fae64312e0e417be7182283870..cb3da62f3ae275eee2a86d3c40aac328a86da90a 100644
--- a/mojo/shell/runner/host/out_of_process_native_runner.cc
+++ b/mojo/shell/runner/host/out_of_process_native_runner.cc
@@ -67,7 +67,8 @@ void OutOfProcessNativeRunner::AppCompleted(int32_t result) {
   // This object may be deleted by this callback.
   base::Closure app_completed_callback = app_completed_callback_;
   app_completed_callback_.Reset();
-  app_completed_callback.Run();
+  if (!app_completed_callback.is_null())
+    app_completed_callback.Run();
 }
 
 void OutOfProcessNativeRunner::OnProcessLaunched(