Regression: LinkWidget no longer supports base fields with optional title

So ::get exits on FieldConfigInterface inherited from ConfigEntityInterface::get, which has nothing to do with BaseFieldDefinitions, fix makes sense to me.

Checked out the docblock on FieldDefinitionInterface::getName:

* Returns the machine name of the field.
*
* This defines how the field data is accessed from the entity. For example,
* if the field name is "foo", then $entity->foo returns its data.

Which is pretty much the exact scenario in the widget, creating a selector to the form element, which matches the access scheme of the entity. The config based implementation is also defined as:

  public function getName() {
    return $this->field_name;
  }

So seems like the correct fix to me and a very low risk change.

Committed to 8.5.x. Thanks!

Didn't take the status :)

@larowlan pointed out that for some reason I forgot to commit this to 8.6.x first. Fixed now!