Goofy message on subscribing to a category

Thank you for taking this on. I installed 5.x-1.x-dev in a 5beta2 site. The only issue I see is that if you subscribe to a category, a white screen is printed with a message of this sort:

taxid = 48 | orgsub = 1

If you reload the page you get the expected display, and the subscription does get recorded.

I'm marking this critical because I'm reluctant to give this to my users.