This should be fixed by 1.5.2.
I've updated and the double forward slashes were gone.
However, instead, I got the word 'activity' in the URL when I tried to access a category from the all activity page.
So, prior updating it was like:
then after update it got:
(which is exactly the same page as: domain.com/politics...)
So I reversed the update.
Instead, I added this line to function qa_path(...) in qa-base.php:
$url = str_replace('//','/',$url);
(just before the return statement)
Now everything is fine! :-)