Fixed "division by zero" error that occurred when considering a CTMC with state rewards but without action rewards

src/storm/generator/PrismNextStateGenerator.cpp

@@ -22,7 +22,7 @@ namespace storm {
         }
         
         template<typename ValueType, typename StateType>
-        PrismNextStateGenerator<ValueType, StateType>::PrismNextStateGenerator(storm::prism::Program const& program, NextStateGeneratorOptions const& options, bool) : NextStateGenerator<ValueType, StateType>(program.getManager(), options), program(program), rewardModels() {
+        PrismNextStateGenerator<ValueType, StateType>::PrismNextStateGenerator(storm::prism::Program const& program, NextStateGeneratorOptions const& options, bool) : NextStateGenerator<ValueType, StateType>(program.getManager(), options), program(program), rewardModels(), hasStateActionRewards(false) {
             STORM_LOG_TRACE("Creating next-state generator for PRISM program: " << program);
             STORM_LOG_THROW(!this->program.specifiesSystemComposition(), storm::exceptions::WrongFormatException, "The explicit next-state generator currently does not support custom system compositions.");
                         
@@ -262,8 +262,10 @@ namespace storm {
                             
                         }
                     }
+                    if (hasStateActionRewards) {
                         globalChoice.addReward(stateActionRewardValue / totalExitRate);
                     }
+                }
                 
                 // Move the newly fused choice in place.
                 allChoices.clear();