orm: Refetch Failure

This addresses an ORM failure where upon refetching an object from the
database that no longer exists the system crashes hard. We use the `one()`
method which expects one result, if there is no result it throws a
`DoesNotExist` exception. We are not catching the exception properly which
crashes osTicket and forces you to clear the session via browser or
database.

include/class.orm.php

@@ -717,9 +717,11 @@ class VerySimpleModel {
     }
 
     private function refetch() {
-        $this->ht =
-            static::objects()->filter($this->getPk())->values()->one()
-            + $this->ht;
+        try {
+            $this->ht =
+                static::objects()->filter($this->getPk())->values()->one()
+                + $this->ht;
+        } catch (DoesNotExist $ex) {}
     }
 
     private function getPk() {