When a library activates the new system preference, ChildNeedsGuarantor and then renews a patron that does not have a guarantor, a 500 error appears. It would more useful to libraries if there was a message explaining why the patron can't be renewed and allowing the library to add the guarantor instead of providing a 500 error. Steps: 1. Turn on ChildNeedsGuarantor 2. Patron (of a patron category that needs a guarantor but doesn't have one linked) gets renewed 3. 500 error appears.