In OE, when the select attribute type is used in a customtag and the Required property is set to true for this attribute, the first item in the selection list is not recognized. A validation error is thrown when attempting to save and insert the tag.

Steps to reproduce

Enable a selection attribute for the align property in the factbox customtag as follows:

Add this block to extension/ezoe/settings/ezoe_attributes.ini

[CustomAttribute_factbox_align]
Name=Align
Default=right
Type=select
Required=true
Selection[]
Selection[left]=Left
Selection[right]=Right
Selection[center]=Center

In the OE field, click the "Insert custom tag" button.

For Tag field, select "factbox"
For the Alight field, select "Left" and click OK

This should produce the following error:

Error: Invalid values entered, these are marked in red.
"Align" is required and must have a value