Headcount value defaulting from null to 0 when Employment Information is changed

Employee has Headcount value blank, this is when we are doing Permanent International Transfer through Interface, where no value is passed for Headcount field. Later Assignment updates are made by Line Manager and we see through Employment Information Change action, even if LM does not have access to Headcount (meaning this field is not visible), post submission of EIC transaction Headcount value is changed to Zero.