fixing defaultCallback method on fields

[binaryk]

Fixed

• fixing defaultCallback method

[what-the-diff]

PR Summary

• Refactored Property Assignment in defaultCallback Method
  This change involves modifying how we're setting up a certain property (think of it as a feature or setting) within the defaultCallback method. Previously, the feature was assigned to $this->defaultCallback. Following this update, the feature is now assigned to $this->fillDefaultCallback. This modification will help in better organization and usage of this feature in the code.