Approvals failing for EEs with No salary

Summary:

Hi All,

We had configured an approval condition based on salary change %. But the transaction is submitted for an EE with no salary it is erroring out. I could write a small piece of code for the null check condition but it appears to be failing. Does anybody have any inputs on how should I provide this null check condition such that for the EEs with no salary also will be passed.

Actual rule:

((Worker's Salary Details.Proposed Change Percentage != null) AND (Worker's Proposed Assignment.result.Worker Type != "C") AND (Worker's Proposed Assignment.result.Worker Type != "N") AND (Worker's Proposed Assignment.result.Business Unit endsWith "NameOfB.U") AND (Worker's Salary Details.Proposed Change Percentage > 10) AND (Worker's Salary Details.Proposed Change Percentage <= 20))