I have this error message, here is the code:

for i = 0 to 3
    day_time = timenow - i * 86400000
    year_ = year(day_time)
    month_ = month(day_time)
    day_ = dayofmonth(day_time)

    [asian_open, asian_close] = get_session_times(year_, month_, day_, asian_open_hour, asian_open_minute, asian_close_hour, asian_close_minute)

    // Draw a rectangle for the Asian session
    if (time >= asian_open and time <= asian_close)
        var box session_box = na
        var label session_label = na  // Define the label variable
        if (time == asian_open)
            session_box := box.new(left=bar_index, top=high, right=bar_index, bottom=low, border_width=1, border_color=color.new(color.gray, 30), bgcolor=session_color)
            session_label := label.new( //here is the error, on the (
                x=bar_index,
                y=high,
                text="Asian",
                xloc=xloc.bar_index,
                yloc=yloc.abovebar,
                textcolor=color.new(color.gray, 0),  // Darker text color
                size=size.small,
                style=label.style_none,
                textalign=text.align_center
            )
        box.set_right(session_box, bar_index)
        box.set_top(session_box, math.max(high, box.get_top(session_box)))
        box.set_bottom(session_box, math.min(low, box.get_bottom(session_box)))
        
        // Calculate the horizontal center of the rectangle
        middle_x = (box.get_left(session_box) + box.get_right(session_box)) / 2
        
        // Center the label horizontally above the rectangle
        label.set_x(session_label, middle_x)
        label.set_y(session_label, box.get_top(session_box) + 10)  // Adjust the vertical position as needed