2.4.0 - Merge paths removes one

[camillemonchicourt]

I want 2 paths (TEST and TEST with orange arrow) that are cut by another path (TEST6, not cut as expalined at #1535).

OK it dont really makes sense to merge 2 paths that are cut by another one and it shouldnt work.
But when merging them, one of the merged paths is deleted.

And TEST6 is now cut in 2.

[LePetitTim]

#1747

Solution :
#1748