dill: no-op on strange fact

Otherwise, if you accidentally give on the system duct, you crash the
event, as in #5138

pkg/arvo/sys/vane/dill.hoon

@@ -278,10 +278,15 @@
           ?-    -.+>.sih
               %poke-ack   ?~(p.p.+>.sih +>.$ (crud %coup u.p.p.+>.sih))
               %kick       peer
-            %watch-ack  ?~  p.p.+>.sih
+              %watch-ack
+            ?~  p.p.+>.sih
               +>.$
             (dump:(crud %reap u.p.p.+>.sih) %logo ~)
-            %fact       (from ;;(dill-blit q:`vase`+>+>.sih))
+          ::
+              %fact
+            ?.  ?=(%dill-blit p.cage.p.+>.sih)
+              +>.$
+            (from ;;(dill-blit q.q.cage.p.+>.sih))
           ==
         ::
             [%clay %note *]