Odd Flow Null Problem

This is a little bizarre I hope someone has seen & solved this before.

Flow logic:

1. Trigger on create/update

2. Get all items that have same Project ID which yields:

{
  "value": [
    {
      "@odata.etag": "\"6\"",
      "ItemInternalId": "163",
      "ID": 163,
      "Title": "?",
      "Project": {
        "@odata.type": "#Microsoft.Azure.Connectors.SharePoint.SPListExpandedReference",
        "Id": 16,
        "Value": "AFRL 711 HPW Sensors"
      },
      "Project#Id": 16,
      "m8sj": "CDO",
      "acuj": 7,
      "mmwk": 2,
      "Modified": DELETED,
      "Created": DELETED,
      "Author": DELETED,
      "Author#Claims": "i:0#.f|membership|wwheeler@cdotech.com",
      "Editor": DELETED ,
     "{Link}": DELETED,
      "{Name}": "?",
      "{FilenameWithExtension}": "?",
      "{Path}": "Lists/Positions/"
    }
  ]
}

- Initialize some variables to hold counts

- Apply to each

 -- Increment billable (Works)

 -- Increment vacancies (Works)

 -- Test to see if vacancies have posts using 

InvalidTemplate. Unable to process template language expressions in action 'Increment_postings' inputs at line '1' and column '2562': 'The template language function 'greater' expects all of its parameters to be either integer or decimal numbers. Found invalid parameter types: 'Null'.'.

This where my noodle gets fried.   Using the very same field  to increment vacancies, it claims to be Null in the greater() function.

Peripheral question why are the field names different than the list definition:

      "m8sj": "CDO",   --> Company
      "acuj": 7,           --> Billable
      "mmwk": 2,       --> Vacant

All suggestions and sympathy welcome!

v/r,

Bill