Mail: Ensure that any `phpmailerException` exceptions generated by `setFrom()`...

Mail: Ensure that any `phpmailerException` exceptions generated by `setFrom()` are caught to avoid PHP Fatal errors.

This change avoids a PHP fatal error that can be encountered when the specified (or generated) source email is an invalid address, such as `wordpress@_`, it makes no effort to set a valid source, only avoid the fatal error.

See #25239 for correcting the email address.
Fixes #39360.

Built from https://develop.svn.wordpress.org/trunk@39655


git-svn-id: https://core.svn.wordpress.org/trunk@39595 1a063a9b-81f0-0310-95a4-ce76da25c4cd