Empty string should be converted to undefined #1168
Description
Describe the bug
We should consider converting empty strings to undefined, because in case of validation errors for non-required properties it can happen that you do not get rid of the error anymore.
To Reproduce
Steps to reproduce the behavior:
Create a schema with a non-required string property with an arbitrary minLength. Delete the respective value of the property in the generated form.
Expected behavior
When clearing the form, the validation message should disappear.
Additional context
Change must be done in the core