Fix a crash bug when running an node without IPv6-exit support.

Fixes bug 7814; bugfix on 0.2.4.7-alpha.

changes/bug7814

@@ -0,0 +1,4 @@
+  o Major bugfixes:
+    - Avoid crashing when, as a node without IPv6-exit support, a
+      client insists on getting an IPv6 address or nothing.  Fixes bug
+      #7814; bugfix on 0.2.4.7-alpha.

src/or/connection_edge.c

@@ -2427,6 +2427,7 @@ connection_exit_begin_conn(cell_t *cell, circuit_t *circ)
       tor_free(address);
       relay_send_end_cell_from_edge(rh.stream_id, circ,
                                     END_STREAM_REASON_EXITPOLICY, NULL);
+      return 0;
     }
   }