Described in #6807 - script is loaded based on current protocol causing issues when caching is enabled (if you switch from http to https the cached page still uses http for script inclusion and thus the browser is blocking it).
Solution
I see no problem in loading it using https all the time. I've also found that &render=explicit is not properly URL encoded and fixed that as well.
Change is good. Please remove whitespaces in line 60!
This comment was created with the J!Tracker Application at issues.joomla.org/joomla-cms/7237.