尝试全局访问'creatureBody'-空值

我正在尝试将我的信息封装在一个变量中，但在我的Corona文件中它很难工作。

我已经删除了更改颜色的行，但我仍然遇到某种功能性错误

function CreateBeast(parent, hasParent)
    hugWall = math.random(4); -- 1 left, 2 top, 3 right, 4 bottom
    red = math.random(255);
    green = math.random(255);
    blue = math.random(255);
    if hugWall == 1 then
        xCoordinates = 0 + radiusCircle;
        yCoordinates = math.random(480);
    elseif hugWall == 2 then
        xCoordinates = math.random(320);
        yCoordinates = 480 - radiusCircle;
    elseif hugWall == 3 then
        xCoordinates = 320 - radiusCircle;
        yCoordinates = math.random(480);
    elseif hugWall == 4 then
        xCoordinates = math.random(320);
        yCoordinates = 0 + radiusCircle;
    end
    if hasParent == 1 then
        creature =
        {
            creatureTitle = parent.creatureTitle;
            size =  parent.size;
            speed = parent.speed;
            x = xCoordinates;
            y = yCoordinates;
            creatureBody = display.newCircle(xCoordinates, yCoordinates, radiusCircle);
            creatureBody:setFillColor(parent);
        }
    else
        creature =
        {
            creatureTitle = creatureIterator;
            creatureIterator = creatureIterator + 1;
            size = 1;
            speed = 1;
            x = xCoordinates;
            y = yCoordinates;
            creatureBody = display.newCircle(xCoordinates, yCoordinates, radiusCircle);
            creatureBody:setFillColor(red, green, blue);
        }
    end
    return creature
end

creatureArray = {};
for i = 0, starterNumOfCreatures , 1
do
    creature = CreateBeast(0,0);
    creatureArray[i] = creature;

end

它一直在抛出尝试访问全局变量的错误。它特别在for循环中创建身体时更改颜色的那一行有问题。谢谢帮忙!