Guard against the role field not being populated

when doing the final reset of Role.implicit_parents.

tools/scripts/ig-hotfix/role_check.py

@@ -180,6 +180,7 @@ def resolve(obj, path):
 print("    obj = cls.objects.get(id=obj_id)")
 print("    for f in role_fields:")
 print("        r = getattr(obj, f.name, None)")
-print("        r.implicit_parents = '[]'")
-print("        r.save()")
+print("        if r is not None:")
+print("            r.implicit_parents = '[]'")
+print("            r.save()")
 print("    obj.save()")