[4.0] [com_fields] setting a default value causes DOMElement error

[stutteringp0et]

Steps to reproduce the issue

1. Create a new field (I tried text, calendar, and one of my own field extensions)
2. type a default value
3. hit save
4. scratch your head (optional)

Expected result

Default set

Actual result

An error has occurred.
0 Class 'Joomla\Component\Fields\Administrator\Plugin\DOMElement' not found

System information (as much as possible)

4.0-dev downloaded yesterday
PHP 7.1.11

Additional comments

Everything else seems to work fine. I can create fields, they work in profiles, data is saved and retrieved - but I just can't seem to set a default value in any of them.

[ghost]

Issue confirmed.

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/19018.}

[stutteringp0et]

Found it - PR will be issued shortly

[joomla-cms-bot]

Set to "closed" on behalf of @franz-wohlkoenig by The JTracker Application at issues.joomla.org/joomla-cms/19018

[ghost]

closed as having Pull Request #19019