views_content_views_empty_content_type_render can't find 'empty' array index

My best assumption right now is that when multiple Views contexts are put together, and one doesn't contain any Empty Text fields, this is triggered.

Changing line 32 of views_content/plugins/content_types/views_empty.inc from:
$block->content = $output['empty'];
to $block->content = !empty($output['empty']) ? $output['empty'] : ''; fixes it; but I'm not aware of where-else the returned $block's data is used. Should this be array(), NULL, or ''?