Fixed OperatorSchedule::getNormalizedWeights bug #758
Fixed OperatorSchedule::getNormalizedWeights bug #758

This method is called by Operator::toString, which may
be called before the weight array required by getNormalizedWeights
is allocated.  This was causing a null pointer exception.

Anaphory/beast2,tgvaughan/beast2,tgvaughan/beast2,Anaphory/beast2,tgvaughan/beast2,CompEvol/beast2,CompEvol/beast2,CompEvol/beast2,CompEvol/beast2,tgvaughan/beast2,Anaphory/beast2,Anaphory/beast2