@Scott, @pupi1985

This fix is written and verified by http://question2answer.org/qa/user/Dan+D. in below thread http://question2answer.org/qa/56966/facebook-login-stopped-working-its-not-even-working-your-site?show=56992#a56992
also see https://github.com/q2a/question2answer/issues/510

I'm just submitting code changes.

Please check line no 593 for currentUrl. 

Thanks to Q2A user Dan D, and Github users valan, iamdand, cksagherian for this patch.