Taxonomy term submit assumes that the value is being provided by a multi value field

Moving back to NW for tests and issue summary updates

Rerolls are fine but if there are outstanding points to be made please keep in NW

I have came across this problem when I was working on one of my projects. I have tried on D10.1 and D11.dev, but the current patch does not solve the problem. Once the $form['relations']['parent']['#multiple']; is set to FALSE, then the $form_state->getValue('parent'); going to return a string value on form submit. Once the form calls buildEntity() it will throw an error because it expects and array value and uses like this: array_values($form_state->getValue('parent'));. Since the return value is going to be a string it will fail. I have came up with a quick fix which will check if the return value is an array or not.

Oops, accidentally removed one line of code which was not intentional. Updated patch uploaded.

Add a minor simplification.