Ability to update the proficiency rating to blank for the Skills in Talent profile thru HDL

Summary:

We have uploaded the Skills thru enhanced talent profile via HDL for both skills attained and skills developing but now we want to make the proficiency blank

Content (please ensure you mask any confidential information):

We have uploaded the Skills thru enhanced talent profile via HDL for both skills attained and skills developing but now we want to make the proficiency blank. As its list of value, thus we tried it with #NULL and even with -999999991 as per Oracle docs as its a numeric rating but still its not making the previous rating as blank even though its not a mandatory value.