エラーの行は
from ******.rb:444:in `open'
from ******.rb:444:in `store_text'

def store_text(lines)
ary = []
lines.each do |line|
ary << line.gsub(/\s+/, ' ').strip　　←ココ　４４４行目
end

ary.each do |line|
@text << line
end

File.open(@text_filename, 'a') do |fp|
ary.each do |line|
line.chomp!

fp.puts line
end