Fix for multiple whitespace characters appearing in the {content} tag

As before, this fixes issues I've been having with a site that places gallery shortcodes at the beginning of their posts.

This causes issues with excess whitespace being left after the strip_tags call, making the automatically generated broadcast message require manual editing a majority of the time.

This change fixes that (whilst maintaining linebreaks) and I don't believe will cause any issues with people who don't experience the issue.

Adrian.