云函数显示调用成功，但是result为空。

打印台输出内容：

{errMsg: "cloud.callFunction:ok", result: null, requestID: "fe516656-722d-11e9-bfae-5254005d5fdb"}errMsg: "cloud.callFunction:ok"requestID: "fe516656-722d-11e9-bfae-5254005d5fdb"result: null__proto__: constructor: ƒ Object()hasOwnProperty: ƒ hasOwnProperty()isPrototypeOf: ƒ isPrototypeOf()nv_constructor: "Object"nv_toString: ƒ ()propertyIsEnumerable: ƒ propertyIsEnumerable()toLocaleString: ƒ toLocaleString()toString: ƒ toString()valueOf: ƒ valueOf()__defineGetter__: ƒ __defineGetter__()__defineSetter__: ƒ __defineSetter__()__lookupGetter__: ƒ __lookupGetter__()__lookupSetter__: ƒ __lookupSetter__()get __proto__: ƒ __proto__()set __proto__: ƒ __proto__()