Fix error when tenant has no licenses

Running on a new tenant with no licenses in use Get-MgBetaSubscribedSku will return with a body of [].

$LicenseInfo was not verifying $SubscribedSku had data before creating the variable that will be used in the report, resulting in a JSON primitive error because the JSON is "license_information":  ,

PowerShell/ScubaGear/Modules/Providers/ExportAADProvider.psm1

@@ -47,7 +47,11 @@ function Export-AADProvider {
     $ServicePlans = $SubscribedSku.ServicePlans | Where-Object -Property ProvisioningStatus -eq -Value "Success"
 
     #Obtains license information for tenant and total number of active users
-    $LicenseInfo = $SubscribedSku | Select-Object -Property Sku*, ConsumedUnits, PrepaidUnits | ConvertTo-Json -Depth 3
+    if ($null -eq $SubscribedSku)
+        {$LicenseInfo = "[]"}
+    else{
+        $LicenseInfo = $SubscribedSku | Select-Object -Property Sku*, ConsumedUnits, PrepaidUnits | ConvertTo-Json -Depth 3
+    }
 
     if ($ServicePlans) {
         # The RequiredServicePlan variable is used so that PIM Cmdlets are only executed if the tenant has the premium license