visually fix daklib.utils.parse_wnpp_bug_file

The file asks Vim to set tabstop=4. So the "lines = []" line formerly
being indented with a tab appears to be executed unconditionally whereas
it really only is executed in the exception handler.

Signed-off-by: Helmut Grohne <helmut@subdivi.de>
Signed-off-by: Helmut Grohne <helmut@subdivi.de>