Restring addition of null supernovae objects to supernovaecomponent list

While loading data for supernovae, there seems error in reading file supernovae.dat so it leads to creation of dummy supernovae object which leads to various error during run time of Kstars. So lets avoid creation of such dummy supernovae objects.
This fixes attached bug too.

Approved by Henry de Valence

FIXED-IN: 4.11.3

REVIEW: 112879