Forward port:
Revert the patch to handle ' ', '.' and '_' equally, as this violates the rule: if a < b and b < c, a must also be < c.
The issue can be reproduced with the strings abc.jpg, abc1.jpg and abc_a.jpg.

I really propose to make this "natural sorting" not more clever than necessary, just handling digits in a "natural" way is sufficient from my point of view.