Fix TypeError when permissionSetGroup has a mutingPermissionSet (#3834)

![image](https://github.com/user-attachments/assets/75aa4450-564a-4fa9-ae81-b200390d71e6)

Fix the issue when the permissionSetGroup has a MutingPermissionSet, So
the type of the PermissionSetId in the PermissionSetGroupComponent will
be of type MutingPermissionSet

Co-authored-by: James Estevez <jestevez@salesforce.com>

Author: lakshmi2506

cumulusci/tasks/preflight/permsets.py

@@ -9,11 +9,14 @@ def _run_task(self):
         for result in self.sf.query_all(query)["records"]:
             if result["PermissionSet"]["Name"] not in self.return_values:
                 self.return_values.append(result["PermissionSet"]["Name"])
-
             if result["PermissionSetGroupId"] is not None:
                 psg_query = f"SELECT PermissionSet.Name from PermissionSetGroupComponent where PermissionSetGroupId = '{result['PermissionSetGroupId']}'"
                 for psg_result in self.sf.query_all(psg_query)["records"]:
-                    if psg_result["PermissionSet"]["Name"] not in self.return_values:
+                    if (
+                        psg_result["PermissionSet"]
+                        and psg_result["PermissionSet"]["Name"]
+                        not in self.return_values
+                    ):
                         self.return_values.append(psg_result["PermissionSet"]["Name"])
 
         permsets_str = "\n".join(self.return_values)