entrynodes.c: fix syntax error around BUG() statement

Fix those misplaced brackets.

Signed-off-by: Martin Kepplinger <martink@posteo.de>

src/or/entrynodes.c

@@ -2372,7 +2372,7 @@ entry_guards_upgrade_waiting_circuits(guard_selection_t *gs,
 
   SMARTLIST_FOREACH_BEGIN(all_circuits, origin_circuit_t *, circ) {
     circuit_guard_state_t *state = origin_circuit_get_guard_state(circ);
-    if BUG((state == NULL))
+    if (BUG(state == NULL))
       continue;
 
     if (state->state == GUARD_CIRC_STATE_WAITING_FOR_BETTER_GUARD) {