Fixes https://github.com/twentyhq/twenty/issues/14548.
When creating a field metadata through the api, the field's icon can be
null (from twenty UI, a default icon is always added by default and it
is not possible to remove it). Then this value is turned into an empty
string in the payload - i don't know why we don't send the null value.
When updating the field through the UI, we run a zod validation that
either accepts a null value for Icon, or a value that starts with
`"Icon".` In our case, the value for Icon was `""` (an empty string),
which is not valid. Therefore the form was considered not valid until an
icon was added.
While the fix suggested works, we should probably sort out the `null`
conversion to `""`, as it is prone to errors.
Marie
53b853f877