修复单挑的get.attitude函数不检测from或to是否存在的问题.

mode/single.js

@@ -1562,6 +1562,7 @@ game.import("mode", function (lib, game, ui, get, ai, _status) {
 		},
 		get: {
 			attitude: function (from, to) {
+				if (!from || !to) return 0;
 				if (from.identity == to.identity) return 10;
 				return -10;
 			},