Date filter shows error in view exposed group filter with multiple select option.

Problem/Motivation

Date views filter (\Drupal\views\Plugin\views\filter\Date) throw a php warning with checked "Allow multiple selections" option.

Warning: Undefined array key "type" in Drupal\views\Plugin\views\filter\Date->acceptExposedInput() (line 128 of core/modules/views/src/Plugin/views/filter/Date.php).

This happens because when the "Allow multiple selections" option is checked the $this->group_infois array.
And this condition in the \Drupal\views\Plugin\views\filter\Date::acceptExposedInput is not enought because $this->group_info['type'] can be an empty and cause a warning:

    if (is_array($this->group_info)) {
        $type = $this->group_info['type'];
    }

Steps to reproduce

1. Install Drupal standard profile
2. Edit the default Content view at /admin/structure/views/view/content
3. Add a "Created" filter
4. Select "Expose this filter to visitors, to allow them to change it"
5. Select "Grouped filters"
6. Set the Grouping 1 label to "Last week", operator to "Is greater than", value type to "An offset from ..." and value "-7 days"
7. Check "Allow multiple selections"
8. Press Apply and then Save
9. Navigate to /admin/content

Proposed resolution

Replace condition in the \Drupal\views\Plugin\views\filter\Date:127
if (is_array($this->group_info)) {
with
if (!empty($this->group_info['type'])) {