Fix generating array with unsorted keys

[ftdebugger]

For example array

$value = array(
    1 => 'a',
    0 => 'b',
    'c'
)

generating to

array(
    1 => 'a',
    'b', // this value will be lost, because it will be rewrite by value 'c'
    2 => 'c'
)

this patch fix it, and do as expected

array(
    1 => 'a',
    0 => 'b',
    'c'
)