Fix bug with email styling on first P

If styles are applied to the first paragraph (by a user) then "first p" breaks the HTML. If custom styles are used this won't try to overwrite them. Reported here - https://easydigitaldownloads.com/support/topic/display-issue-in-the-receipt/
Merge pull request #1682 from elliott-stocks/patch-8

Fix bug with email styling on first P