尝试给全局变量（nil值）索引时发生了冲突。

当我尝试与 BCloud1.png 床发生碰撞时，我得到了一个尝试索引全局变量 'BCoud1'（一个空值）的错误？ 是否有任何解决此错误的简单方法？

我已经做了这个：

function getRandomStar()
    local temp = starTable[math.random(1, #starTable)] --从 starTable 获取随机星星
    local randomStar = display.newImage(temp.imgpath) --设置对象的图像路径

    if (temp.imgpath == "BCloud1.png") then
        temp.imgpath = "BCloud"..tostring(math.random(1, 3))..".png";
        physics.addBody(BCloud1, {density=3.0, friction=0.5, bounce=0.3})
    end

    if (temp.imgpath == "BCloud2.png") then
        temp.imgpath = "BCloud"..tostring(math.random(1, 3))..".png";
        physics.addBody(randomStar, "static", {density=.1, bounce=.1, friction=.2, radius=45})
    end

    if (temp.imgpath == "BCloud3.png") then
        temp.imgpath = "BCloud"..tostring(math.random(1, 3))..".png";
        physics.addBody(randomStar, "static", {density=.1, bounce=.1, friction=.2, radius=45})
    end

    randomStar.myName = "star" --将对象的名称设置为“星星”
    randomStar.movementSpeed = temp.movementSpeed; -- 设置对象移动的速度
    randomStar.x = math.random(-30, _W);
    randomStar.y = -35;
    randomStar.rotation = math.random(0,20) -- 旋转对象

    starMove = transition.to(randomStar, {
        time=randomStar.movementSpeed,
        y=500,
        onComplete = function(self) self.parent:remove(self); self = nil;
        end
        }) -- 移动星星
end--END getRandomStar()

local function onLocalCollision1(self, event)
    if (event.phase == "began") then
        print("Collision1")
    elseif (event.phase == "ended") then
    end
end
BCloud1.collision = onLocalCollision1
BCloud1:addEventListener("collision", BCloud1.png)