Add unique case for null passives in status hitrate calculation

Assuming I correctly understand the math behind this. An entity with a Null Status Passive currently has a 1/101 chance of being inflicted with the passive(The 1/101 comes from 0 being included in the range and the only case where the if statement could be satisfied in this situation). Since this likely is not the intended mechanics, status_hitrate is now checked to ensure its larger than 0 to begin with before successfully inflicting a status effect.