Stage is not displayed when engines are not linked to a tank with a native attach point (but the game does)

[OnlyLightMatters]

Hi!
I open this issue after a discussion in the mod's thread:
https://forum.kerbalspaceprogram.com/index.php?/topic/17833-130-kerbal-engineer-redux-1130-2017-05-28/&do=findComment&comment=3903427 (and below)

It has been tested on 1.10.1 with KER 1.1.7.2 and 1.11.0 with KER 1.1.8.2.

The screen capture shows that in specific ship constructions, KER seems not to detect an engine is provided with fuel so does not consider the whole thing as a functionnal stage.
You can recreate the example with the following how-to.

1. Pick any part which is not a fuel tank and cannot be radially attached (here a storage unit)
2. Put 2 cubic struts on it.
3. Most important: reroot to one of the cubic strut.
4. Attach an engine to one, a fuel tank to the other.
5. Finish the craft

With different words, the bug happens when an engine is not linked to a fuel tank via one or more native attach points.

I think this is an old behavior of the mod which may have been consistent with the game at one point.

Special words: thank you so much for supporting this mod. It has been the first I have ever installed and it has never left me since then :)