Check KerbalRef before calculating contribution.

It seems KerbalRef can be null (it's the only way to get an NRE in
KerbalContribution).
Rework craft spawning to avoid twisted ships.

Many thanks to angavrilov for his tips. It turns out I need to wait for the
parts to initialize properly before docking the vessel to the pad. There
are still some issues (not warping through the spawn causes not-so-rapid
unplanned disassembly, warping though the spawn avoids that but the orbit
renderer seems to be messed up), but this is good progress towards fixing
issue #3.