Plug gcc warning after r268074 about unitialized newsigacts

Reported by:	Gary Jennejohn <gljennjohn gmail.com>

sys/kern/kern_exec.c

@@ -623,8 +623,10 @@ do_execve(td, args, mac_p)
 		oldsigacts = p->p_sigacts;
 		newsigacts = sigacts_alloc();
 		sigacts_copy(newsigacts, oldsigacts);
-	} else
+	} else {
 		oldsigacts = NULL;
+		newsigacts = NULL; /* satisfy gcc */
+	}
 
 	PROC_LOCK(p);
 	if (oldsigacts)