* Fix fax_queue to Email PDF Instead of TIF
Variables `$fax_file_tif` and `$fax_file_pdf` are missing a period before the extension so file_exists is always evaluating to false. Thus, TIF was always sent. Adds the period back into the path so the check works correctly.
NOTE: `$fax_file_tif` is completely unused and can be removed from this code for cleanup.
* Use single quotes.