when does output of get_user_count turns into an array?

Via:

• http://lists.automattic.com/pipermail/wp-hackers/2012-June/043295.html
• http://wordpress.org/support/topic/illegal-string-offset-total_users?replies=14#post-2893756
• https://core.trac.wordpress.org/ticket/20966

I find:

1. Normally it would return an array from the cache
2. Meaning the return value of get_user_count() is different than in the php doc above it
3. But… if the cache does not contain it, it will return an integer leading (in my case)
   to an warning (requesting an array value from a string) BUT somehow not leading to
   a warning with many others (assuming they still have an array as return value, even if
   it does not contain a value)

I found out that when on PHP version 5.4 or later it will throw this warning. Previous versions will not throw this warning, related, see example 2 on http://php.net/manual/en/function.empty.php

It has been taken care of in 20966