Small fixes and invert colors range

TODO: more encoding issues.
Fix race condition: long shutdown on error

If queue is flushed quickly enough, check_error never happens until all queue
items are pushed. Move check_error to the beginning of the loop to fix this.

Also set join timeout to 0.2 to speed up shutdown on error.
Simple integrity check

Match newpage and airport code in single RE; check that at least one page is
present.
Fix previous commit 1-page case
Popup message box when error occurs

Currently simple message box asking to check logs.