Uploading file to NodeMcu: some error after modified the code.

[piebat]

I'have this code:

-- LUA module for writer-reader hardware MFRC522 -
local mfrc = {}
function mfrc.foo()
    print("salve mondo!")
end

return mfrc

It goes well and it is loaded on NodeMcu without error
but if i modify in:

-- LUA module for writer-reader hardware MFRC522 
local mfrc = {}
function mfrc.foo()
    print("salve mondo!")
end

return mfrc

it cannot be loaded because give error!
Have you see the difference in line 1 ( I cancel a '-' )
The most interesting thing is that if I add again the 'dash' character at end of first line... it work again!
Ok I did other test.. not exhaustive, but until now I suspect something related to the numbers of characters in the first line.