Error handeling when sparsifying in makePSN_NamedMatrix.R

[AnneKrogh]

1. An error should be returned if the cutoff is higher than the pat_pairs values in makePSN_NamedMatrix.R.
2. An error should be returned if an error occurs in one of the iterations in the parallel processing (foreach loop line 99 in makePSN_NamedMatrix.R)
3. netDx should stop running if an error occurs when sparsifying.