lnmtl.com terminates when chapter_no not purely numeric

[mchubby]

Visiting: https://lnmtl.com/chapter/the-amber-sword-book-3-chapter-531-1
Traceback (most recent call last):
  File "/usr/lib/python3.6/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/lib/python3.6/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "./__main__.py", line 74, in <module>
    main()
  File "./__main__.py", line 28, in main
    end_url=sys.argv[4] if len(sys.argv) > 4 else ''
  File "./EbookCrawler/lnmtl.py", line 57, in start
    self.crawl_chapters(browser)
  File "./EbookCrawler/lnmtl.py", line 89, in crawl_chapters
    self.parse_chapter(browser)
  File "./EbookCrawler/lnmtl.py", line 112, in parse_chapter
    chapter_no = re.search(r'chapter-\d+$', url).group().strip('chapter-')
AttributeError: 'NoneType' object has no attribute 'group'

There are two chapters labeled # 531 on the website.

[dipu-bd]

This issue is fixed with the latest push