Deleting sprites causing problems in Corona SDK

[thyrgle]

I have an array called toRemove:

local toRemove = {}

I have a group called enemies which stores the enemy sprites and I have a collision detection function that looks like this:

local function onCollision( self, event )
    --Bullet hit enemy
    if self.name == "bullet" and event.other.name == "enemy" then
        table.insert(toRemove, event.other)
    end
end

It is getting inside the if statement. I have a game loop:

local function gameLoop ( event )

    for i = 1, #toRemove do
        toRemove[i].parent:remove(toRemove[i]) --This is line 158 (important to know later)
        toRemove[i] = nil
    end
end

This gameLoop function is invoked like so:

Runtime:addEventListener( "enterFrame", gameLoop )

When I run my program it says:

...main.lua:158: attempt to index field 'parent' (a nil value)

When I modify my game loop as follows:

local function gameLoop ( event )

    for i = 1, #toRemove do
        print(toRemove[i].parent)
        --toRemove[i].parent:remove(toRemove[i]) --This is line 158 (important to know later)
        toRemove[i] = nil
    end
end

Nothing crashes (although no sprite is removed), and it prints:

table: <memory Address>

Why wont it let me remove the parent?