Weird crystal error

example.cr

f = File.new("buffer_i_gen_batt.txt")

6.times do
  _ = f.gets
end

interval = f.gets

def real_val(raw_val)
  (raw_val - 520) * 0.191
end

def normalize
end

loop do
  break unless n = f.gets

  unless n.to_s == ""
    puts n.to_s.to_i
  end

  # puts n.to_i
end

unless line == "" instead of if

file = File.open("buffer_i_gen_batt.txt")

values = Array(Float64).new

meas_offset = -512
linear_coefficient = 0.191

6.times do
    file.gets
end

interval = file.gets.to_s.to_i
puts interval

file.each_line do |raw_line|
    line = raw_line.to_s.strip
    puts line.inspect
    unless line == ""
        raw_value = line.to_i
        # real_value = (raw_value + meas_offset) * linear_coefficient
        # values << real_value
        # puts real_value
    end
end

file.close

min_value = values.min

values.each do |value|
    value -= min_value
end