Error sending email with reply-to 1

Problem/Motivation

After installing the module I got:
Error sending email (from *** to *** with reply-to 1).
After debugging I found:

      $this->mailManager->mail('admin_content_notification', $key, $admin_email, 'en', $params, TRUE);

however mail exepts string|null, not TRUE.

Proposed resolution

Will provide the patch.

Remaining tasks

None.

User interface changes

None.

API changes

None.

Data model changes

None.

Release notes snippet

None.