CRM_Mailing_BAO_Mailing was changed in 4.7.13

[drifteaur]

Since upgrading to CiviCRM 4.7.13 I'm getting a Call to undefined method CRM_Mailing_BAO_Mailing::getPublicViewUrl() when viewing mailing reports.

[eileenmcnaughton]

This is why the recommendation is not to ever do php overrides in extensions.... :-(