graph: Cycle check ignores Zero entries.

src/storm/utility/graph.cpp

@@ -141,6 +141,7 @@ namespace storm {
                         if (unexploredStates.get(state)) {
                             unexploredStates.set(state, false);
                             for (auto const& entry : transitionMatrix.getRowGroup(state)) {
+                                if (!storm::utility::isZero(entry.getValue())) {
                                     if (unexploredStates.get(entry.getColumn())) {
                                         dfsStack.push_back(entry.getColumn());
                                     } else {
@@ -150,6 +151,7 @@ namespace storm {
                                         }
                                     }
                                 }
+                            }
                         } else {
                             acyclicStates.set(state, true);
                             dfsStack.pop_back();