⚠ 0 cm at top of profile

This issue was reported by Scott Thumlert.

Steps to reproduce the problem:

1. Try to draw any profile
2. Enter first layer with 0 and then larger number

Expected result: that it would be possible to create a profile with 0 at the top. This is very useful when profiles are not dug to ground.

Actual result: not able to enter a layer with smaller number at top and larger at bottom.