As described here [https://discussions.unity.com/t/unset-reset-or-clear-integerfield-inputfield-numericfield-and-manage-placeholder-issue-and-solution/1690089]

Resetting of an IntegerField currently not possible by code, like setting integerField to null.
one can set the value to a default value but placeholder style of empty field not recovered (like when deleting the input with keyboard); 

Steps to reproduce:

1. Create an IntegerFiled
2. try to set the value to null/default

Actual results: 

Can't do it and the placeholder is hidden

Expected results: 

We have a way to reset the value and see the placeholder

Reproducible with versions:  6000.3.0b5

Not reproducible with versions: 

Can’t test with versions: 

Tested on (OS): windows

Notes:

• For numeric fields, setting to null is not an option. We'll need a method to clear the field. The `text` property would have been an option, but it's internal.