Attempting to set a negative margin-top of half height using sass maps. The units returning don't appear to be a string or integer.

map-division.scss

// Generated from spritesmith via gulp

$sprites: (
    arrow-right-blue-withShadow: (
        x: 0px,
        y: 114px,
        offset_x: 0px,
        offset_y: -114px,
        width: 13px,
        height: 19px,
        total_width: 239px,
        total_height: 799px,
        image: '../img/icon-sprite.png'
    ),
    arrow-right-white-withShadow: (
        x: 0px,
        y: 233px,
        offset_x: 0px,
        offset_y: -233px,
        width: 13px,
        height: 19px,
        total_width: 239px,
        total_height: 799px,
        image: '../img/icon-sprite.png'
    ),
    club-evolution-191x40: (
        x: 0px,
        y: 596px,
        offset_x: 0px,
        offset_y: -596px,
        width: 191px,
        height: 40px,
        total_width: 239px,
        total_height: 799px,
        image: '../img/icon-sprite.png'
    ),
);


@function sprite($sprite, $attribute) {
    @return map-get(map-get($sprites, $sprite), $attribute),
}

/* */

$iconHeightSprite: sprite(arrow-right-blue-withShadow , 'height');


/*
Failed attempts:
@function strip-units($number) {
  @return $number / ($number * 0 + 1);
}

$iconHeightSprite: unquote($iconHeightSprite);
@warn strip-units( $iconHeightSprite ); //    error scss/example.scss (Line 50: Undefined operation: "19px times 0".)
*/




$iconHalfHeight: $iconHeightSprite/2;

.example {
    margin-top: $iconHalfHeight;
}