Support OCBC bank statement

[Wei Lu]

Traceback (most recent call last):
  File "/var/task/chalice/app.py", line 659, in _get_view_function_response
    response = view_function(**function_args)
  File "/var/task/app.py", line 139, in upload
    env=dict(LD_LIBRARY_PATH=LIB_DIR))
  File "/var/task/chalicelib/pdftotxt.py", line 131, in process_pdf
    process_line(iter(lines), statement_date)
  File "/var/task/chalicelib/pdftotxt.py", line 118, in process_line
    process_line(iterator, statement_date)
  File "/var/task/chalicelib/pdftotxt.py", line 118, in process_line
    process_line(iterator, statement_date)
  File "/var/task/chalicelib/pdftotxt.py", line 118, in process_line
    process_line(iterator, statement_date)
  [Previous line repeated 16 more times]
  File "/var/task/chalicelib/pdftotxt.py", line 110, in process_line
    date = parse_transaction_date(groups[0], statement_date)
  File "/var/task/chalicelib/pdftotxt.py", line 55, in parse_transaction_date
    transaction_date = parse_date(date_str).replace(year=statement_date.year)
AttributeError: 'NoneType' object has no attribute 'year'