Not properly copying empty blocks inside object methods

[drkameleon]

Describe the bug

define :queue [
    init: method [][
        this\items: []            <----- INITIAL ASSIGNMENT
    ]

    enqueue: method [item][
        panic "enqueue must be implemented by concrete type"
    ]

    dequeue: method [][
        panic "dequeue must be implemented by concrete type" 
    ]
]

define :simpleQueue is :queue [
    enqueue: method [item][       
        'this\items ++ item       <----- THIS ALTERS `[]` ITSELF !!!!!
        print "ENQUEUE"
        print size []             <----- THIS IS NOT AN EMPTY BLOCK ANYMORE
        inspect []
    ]

    dequeue: method [][           <----- NOT EVEN THAT IS AN EMPTY BLOCK?!
        if empty? this\items -> return null
        pop 'this\items
    ]

]

; Usage example
q: to :simpleQueue []!
inspect q
inspect to :bytecode [
    q\enqueue "first"
]
q\enqueue "first"
q\enqueue "second"

inspect to :bytecode [
    q\dequeue       ; first
]
q\dequeue
q\dequeue       ; second
q\dequeue       ; null