Fix issue when using inside a Joomla website

[fstn]

Description

DomElement is not define on key $constructor

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• [X] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update