Error while using FILTER/DESCRIPTOR_IDOF in formula with multiple subject areas

Summary

The logical column referenced by DESCRIPTOR_IDOF does not specify a Descriptor ID column

Content

I'm trying to summarize Headcount based on Gender, Ethnicity and Person Legislative Attribute Values but it's only working for Gender. 

When filtered with Ethnicity it is returning 0 which is not the expected value.

When filtered with Person Legislative Attribute it is throwing error. The logical column referenced by DESCRIPTOR_IDOF does not specify a Descriptor ID column

Is there any issue with my formulas? Any alternative options to meet my objective?

Attached the XML for reference.

Code Snippet

<saw:report xmlns:saw="com.siebel.analytics.web/report/v1.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:sawx="com.siebel.analytics.web/expression/v1.1" xmlVersion="201201160" appObjectID="a714deff-7b09-4229-9a2d-aa4598135cce~11.13.20.10.0.0">  
   <saw:criteria xsi:type="saw:simpleCriteria" subjectArea=""Workforce Management - Worker Assignment Real Time"" withinHierarchy="true">    
      <saw:columns>      
         <saw:column xsi:type="saw:regularColumn" columnID="ce7115482a6bd1be7">        
            <saw:columnFormula>          
               <sawx:expr xsi:type="sawx:sqlExpression">IFNULL("Worker Assignment"."Head Count",0)</sawx:expr>