Issue #3495899: Fix the view edit form crash when the reference display is not...

Issue #3495899: Fix the view edit form crash when the reference display is not an Entity Reference display

Any other display type renders the whole view as one render array instead of rows keyed by entity id, so building the options failed and the view edit form could no longer be opened. Return NULL and log a warning for such a display, and add a kernel test.

Closes #3495899