Easyforms: generated field name is not retained

There is a bug retaining field names when creating fields in easy forms.

Reproduction scenario:

• Create a field and type a name in the label, the field name is then generated
• Add another field, give it a name, again the value field_name is replaced with the generated/derived name from the label.
• Save the form.

When reopening the form the second field has not retained the generated value but has reverted to 'field_name'.