This question has been answered by BobRay. See the first response.
return '';
return '';
I've got this happening on migxCalendars and was wondering where that 1 was coming from. Will have to dig through the site and see if it appears elsewhere.Until this gets fixed permanently in the core, and/or plugins get updated, look through the code of all your plugins in the Elements tree, as well as snippets. If there is no "return" statement at the end, just add it as Bob said. I did that and found two plugins that didn't have return at the end, and it fixed the problems for me.