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.

Signed-off-by: Jason Boyer <jboyer@library.in.gov>