Restrict number of BlimpContents to [0, 1]

blimp/client/core/blimp_client_context_impl.cc

Index: blimp/client/core/blimp_client_context_impl.cc
diff --git a/blimp/client/core/blimp_client_context_impl.cc b/blimp/client/core/blimp_client_context_impl.cc
index 4ebebde648c30cfb8a3c03536604343eb4b982d8..2795e16a6550b3f4b60423f253472c5992c898e3 100644
--- a/blimp/client/core/blimp_client_context_impl.cc
+++ b/blimp/client/core/blimp_client_context_impl.cc
@@ -88,7 +88,8 @@ void BlimpClientContextImpl::SetDelegate(BlimpClientContextDelegate* delegate) {
 std::unique_ptr<BlimpContents> BlimpClientContextImpl::CreateBlimpContents() {
   std::unique_ptr<BlimpContents> blimp_contents =
       blimp_contents_manager_->CreateBlimpContents();
-  delegate_->AttachBlimpContentsHelpers(blimp_contents.get());
+  if (blimp_contents)
+    delegate_->AttachBlimpContentsHelpers(blimp_contents.get());
   return blimp_contents;
 }