Missing context erroneously results in View showing all results

To reproduce:

1. Configure a Views content pane view to get a contextual filter value from a context. Configure the argument to "Hide view" when the contextual filter is not available.
2. Embed the view in a panel and assign its argument a context that may or may not exist (such as a context derived from a relationship that stems from an optional field)
3. Observe that, when the context is missing, the view still displays and shows all results.

Expected behavior: View would not display because the contextual filter is missing.

This is caused by code in views_content_views_panes_content_type_render() that falls back to the "all" value for a views contextual filter if the context is missing. The bug only exists when you've configured the view to receive its contextual filter via a context; it behaves correctly when passed in via keywords or other approaches.