Explicitly check for HUP in proxy_recv, avoiding an attempt at reading a line

src/generator.c

@@ -1978,6 +1978,9 @@ static void *proxy_recv(void *arg)
 		if (likely(ret > 0)) {
 			subproxy = event.data.ptr;
 			cs = subproxy->cs;
+			if (event.events & EPOLLHUP)
+				ret = -1;
+			else
 				ret = read_socket_line(cs, 5);
 		}
 		if (ret < 1) {