Issue description
In the screenshot below, you can see two high pressure turbines, connected via mechanical shaft to 4 power generators, which are then connected to ghost low pressure turbines, then connected to 2 more power generators. All 6 power generators are spinning from the shaft connected to the HPTs. The two LPTs are ghosts; the "shaft" should not exist yet because they have not been built, thus the 2 PGs to the left should not be spinning and should not be generating power.

Reproduction steps
- Reproduce scenario as shown in screenshot
- Observe PGs spinning while connected to "ghost shaft"
Game version and build number
v0.5.4f
Operating system
Windows