examples/web-file-browser: Add comment about why it's an assert() and not something weaker.
examples/web-file-browser: Add comment about why it's an assert() and not something weaker.

dropbox/dropbox-sdk-php,demisang/dropbox-sdk-php,itsazzad/dropbox-sdk-php,TimeDoctorLLC/dropbox-sdk-php,sayfulit/dropbox-sdk-php,dropbox/dropbox-sdk-php,demisang/dropbox-sdk-php,itsazzad/dropbox-sdk-php,TimeDoctorLLC/dropbox-sdk-php,sayfulit/dropbox-sdk-php