Undefined array key "_none"

@promes, can you please provide the steps to reproduce the issue.
I used the name field and created content using 1.x-dev version but found no warnings.

I have a name field where a title is required. The '-- --' option is not present, but only other options. So the [_none] => -- is not present as select option when function name_element_render_component() is called.

I was wrong. Line 467 should read:
if (isset($element['#options']['_none']) && $element['#options']['_none']) {

I think the issue is a duplicate of this Issue 🐛 Literal "_none" value saved for seelct fields Active

I have created the patch pleas review it