Depths were being calculated incorrectly due to MIC distance getting
divided by scaling factor rather than multiplied by it.
The scaling factor is the inverse of the tan of half the cutting tool
angle, so for a 30 degree bit (say), the scaling factor would be
1 / tan(30/2), or 3.7320.
When given an MIC (which is a radius) of 3.175 (say), and cutting to the
same width with a 30 degree bit, the depth should be 3.175 * 3.7320
(11..849), not 3.175 / 3.7320 (0.8509) as it is currently.
Identified by MLampert. If multiple faces are selected at varying Z-heights, the `combineConnectedShapes()` method fails to connect them due to offset Z-heights. This fix places all input faces for that method into the same working plane.
When profiling open edges, the user must currently select a top edge and then set the Final Depth manually to a value below the selected edge(s).
This fix provides the user with feedback for the empty path generated.