title: Users delta collection returns "empty" records
body: <p>We are trying to call this MS Graph endpoint: </p>
  
  <pre><code>https://graph.microsoft.com/v1.0/users/delta?$deltatoken=&lt;DELTA_TOKEN&gt;&amp;$select=id,displayName,givenName,surname,employeeId,accountEnabled,assignedLicenses,assignedPlans,licenseAssignmentStates,usageLocation,userPrincipalName,userType,businessPhones,mail,mailNickname,mobilePhone,proxyAddresses,streetAddress,city,country,companyName,department,jobTitle,officeLocation,postalCode,state,isResourceAccount,createdDateTime,deletedDateTime,lastPasswordChangeDateTime,onPremisesLastSyncDateTime,onPremisesDistinguishedName,onPremisesDomainName,onPremisesImmutableId,onPremisesSamAccountName,onPremisesSecurityIdentifier,onPremisesSyncEnabled,onPremisesUserPrincipalName
  </code></pre>
  
  <p>This is what we get:</p>
  
  <pre><code>"value": [
      {
          "displayName": "Jozef Surname",
          "givenName": "Jozef",
          "surname": "Surname",
          "userPrincipalName": "jozef.surname@company.com",
          "mail": "jozef.surname@company.com",
          "id": "048...3d-eaf2-4199-8e88-9cd6...2091b"
      },
      {
          "displayName": null,
          "givenName": null,
          "surname": null,
          "userPrincipalName": null,
          "mail": null,
          "id": "ae...ecf-8ae8-4666-b158-93...c799c00"
      },
      {
          "displayName": null,
          "givenName": null,
          "surname": null,
          "userPrincipalName": null,
          "mail": null,
          "id": "33...d09-81a9-4304-833d-71...92f4b6a"
      },
  </code></pre>
  
  <p>The question is, why are we getting records with null fields? We would expect records like the first one in above example. 
  When we query for some empty record (record with nulls) (<a href="https://graph.microsoft.com/v1.0/users/ae...ecf-8ae8-4666-b158-93...c799c00" rel="nofollow noreferrer">https://graph.microsoft.com/v1.0/users/ae...ecf-8ae8-4666-b158-93...c799c00</a>), we get this:</p>
  
  <pre><code>{
  "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#users/$entity",
  "businessPhones": [],
  "displayName": "Zuzana Surname4",
  "givenName": "Zuzana",
  "jobTitle": null,
  "mail": "zuzana.surname4@company.com",
  "mobilePhone": null,
  "officeLocation": null,
  "preferredLanguage": null,
  "surname": "Surname4",
  "userPrincipalName": "zuzana.surname4@company.com",
  "id": "ae...ecf-8ae8-4666-b158-93...c799c00"
  </code></pre>
  
  <p>}</p>
  
  <p>It’s an existing user. We just don’t know why it’s returned with null fields when we call /users/delta with deltaToken?</p>
  
  <p>We would expect a response like this one (no “empty” records):</p>
  
  <pre><code>"value": [
      {
          "displayName": "Jozef Surname",
          "givenName": "Jozef",
          "surname": "Surname",
          "userPrincipalName": "jozef.surname@company.com",
          "mail": "jozef.surname@company.com",
          "id": "04...33d-eaf2-4199-8e88-9c...b82091b"
      },        
      {
          "displayName": "Nick Surname2",
          "givenName": "Nick",
          "surname": "Surname2",
          "userPrincipalName": "nick.surname2@company.com",
          "mail": "nick.surname2@company.com",
          "id": "4f...faa-f1eb-462b-be31-e5...5860a25"
      },                
      {
          "displayName": "Jan Surname3",
          "givenName": "Jan",
          "surname": "Surname3",
          "userPrincipalName": "jan.surname3@company.com",
          "mail": "jan.surname3@company.com",
          "id": "25...f04-dbec-4580-b35b-3a...262b38c"
      },
  </code></pre>
  
  <p>Is this a bug in /users/delta with deltaToken or is it expected behavior?</p>
  
  <p>Thanks for any help.</p>