Passing any argument to an `/image` subtype constructor should override all subtype definitions

[amylizzle]

https://www.byond.com/forum/post/2923118

/image/subtype
    alpha = 100

/proc/main()
    var/image/subtype/a = new /image/subtype
    var/image/subtype/b = new /image/subtype("test_arg")

    world.log << a.alpha
    world.log << b.alpha

BYOND outputs

100
255