ValueMap报错

Program: …ocos\PopStar\proj.win32\Debug.win32\libcocos2d.dll
File: D:\cocos\PopStar\cocos2d\cocos\base\CCValue.cpp
Line: 745

Expression: _type == Type::MAP

For information on how your program can cause an assertion
failure, see the Visual C++ documentation on asserts
这是错误信息
Point tiledPos = tileCoordForPosition(Point(dstPos.x, dstPos.y));
int tiledGid = meta->getTileGIDAt(tiledPos);//获取这个格子的唯一标识

//判断这个格子是否存在
if (tiledGid != 0) {
	
	Value properties = m_map->getPropertiesForGID(tiledGid);

	ValueMap propMap = properties.asValueMap();//每次执行这一句的时候就会报错

	if (propMap.find("Collidable") != propMap.end()) {
		//获取格子的Collidable属性
		Value prop = propMap.at("Collidable");
		if (prop.asString().compare("true") == 0) {
			//发现这个格子属性为true,不让玩家继续移动
			return true;
		}
	}
	 
}
return false;//反之,返回false

这是具体代码