LP1790896: Receipt Errors with invalid emails

LP1790896: Receipt Errors with invalid emails

The attempt at belt-and-suspenders checking for a valid
email for use in the has_email template field sadly
causes the JS to trip over said suspenders if there is
a value in the field but it doesn't contain a '@'.

The raw return from "".match() (either an array or null)
is enough to do the right thing when converted into a
Boolean and doesn't cause the same problems.

To test
-------
[1] Set up a patron record with an invalid email address,
    e.g., one that lacks the '@' character.
[2] Check out an item the patron, then from the Items Out
    tab, print an item receipt.
[3] Note that nothing happens and an error is logged in the
    browser console.
[4] Apply the patch and repeat step 2. This time, a receipt
    should be generated.

Signed-off-by: Jason Boyer <jboyer@library.in.gov>
Signed-off-by: Josh Stompro <stompro@stompro.org>
Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>