Some symbols in the `keyboard` object don't reset to `0` when the keys are released

[Skaruts]

I was in the process of updating an input mapper I made a while ago, and I came across this issue with the @ symbol and some others.

object
    2 = 0
    ALT_RIGHT = 0
    ALTGRAPH = 0
    DIGIT_2 = 0
    @ = 1          // <----- it hasn't been reset
    (...)
end

In my case, it seems to only affect the symbols that I need AltGr for (right-alt). My keyboard is Portuguese, so for me that's all of these symbols @ £ § € { [ ] } € ¨.

This is currently breaking my input mapper, at least on Portuguese keyboard layouts. I mean, it works for the most part, but will break if a user uses these symbols.