Steps to reproduce

1. Install Ibexa DXP 3.3/eZ Platform 2.5
2. Create a new CT with an email field
3. Create content and enter the email with upper letter case e.g. test@TEST.com
4. Publish
5.  Try to run the command php bin/console ibexa:reindex

Result

The error is displayed: Notice: Undefined index: test@TEST.com
at the same time, it is not possible to perform a reindex

Expected

the ability to add new content without any problem and the ability to correctly index existing content