improve $commandOutput processing

eng/common/scripts/get-codeowners.ps1

@@ -123,13 +123,13 @@ function Get-Codeowners(
     return ,@()
   }
 
-# Assert: $commandOutput is a valid JSON representing a single CodeownersEntry, or an empty string.
+# Assert: $commandOutput is a valid JSON representing:
+# - a single CodeownersEntry, if the $targetPath was a single path
+# - or a dictionary of CodeownerEntries, keyes by each path resolved from a $targetPath glob path.
+#
+# For implementation details, see Azure.Sdk.Tools.RetrieveCodeOwners.Program.Main
 
-  $codeownersJson = $commandOutput | ConvertFrom-Json
-  if (!$codeownersJson) {
-    Write-Host "No code owners returned for the path: $targetPath"
-    return ,@()
-  }
+$codeownersJson = $commandOutput | ConvertFrom-Json
 
   if ($VsoVariable) {
     $codeowners = $codeownersJson.Owners -join ","