Fix T87991.

To inset a face in Orthographic view variable, amount returns negative value for present logic.

To improve inset function for such small case, following changes were made.

variable is_not_front used to check using pixel value if selected face is facing towards screen.
If bool value is true, set initial length 0.

Definitely this is not the proper way to fix the issue.

Note: Patch is not ready for review, some improvements required here.