Units refuse to enter formation

[elexis]

In this r23670 replay units received a formation order, then move orders. Then new units were trained, selected along with the existing formation. The GUI said they were not in formation, clicking on the formation did not make them enter formation. This happens at minute 1 in the replay.

I didn't have time to isolate the bug, hopefully it's a user error.

[Freagarach]

So far, I have narrowed this down to something I wanted to report earlier. What happens is that a formation is trying to be made at turn 290, but there is one entity (entity 168, good luck visually finding that one, it is hidden underneath entity 181) that is not included in the same cluster as the rest. This causes the formation to disband, since the one entity cannot be set to a formation and thus both clusters can't be set.

This means two things are noticed herein:

• Why does Command.txt/ClusterEntities exclude that one entity from the main cluster? <- A real bug.
• When having one cluster large enough to form a formation, and another one which can't, the user expects the one that can to actually form the formation. (This can be tested easier by having two units close by and one far of (at least 60 m), selecting all three units and trying to set them to a formation.

[Silier]

In 23693:

Fix computation of clusters and var->let

Compare matrix values against undefined instead of relying on || because || does not work as intended when distance is 0.

Differential Revision: ​https://code.wildfiregames.com/D2761
Fixes: #5761