♥ ♥ rendering in Gmail Mails [closed]

I am currently testing sending an (HTML) email using PHP via SMTP. Everything is working fine so far - but I’ve discovered a small issue:

I inserted a short text snippet (see example here) into the footer, which includes a ♥ (♥) placed between words. None of the email clients have any trouble with this; only Gmail breaks the line, turning a single line into three.

What is causing this and how I can work around it?

(All Mailclients)

(Gmail)