marionettejs/backbone.marionette — pull request #2025 by duncanbeevers (2014-10-26 14:59:19+00:00)
Title: Allow non-DOM-backed regions

Factor error-throwing out of _ensureElement to _throwOnMissingRegionElement
Spec overriding _throwOnMissingRegionElement to no-op
_ensureElement returns boolean, indicating whether or not element is available
Region#show early-terminates on missing element