changed isValid function

corsika/detail/framework/core/Cascade.inl

corsika/detail/modules/pythia8/Interaction.inl

corsika/detail/modules/qgsjetII/InteractionModel.inl

corsika/detail/modules/sibyll/Decay.inl

corsika/detail/modules/sibyll/InteractionModel.inl

corsika/detail/modules/sibyll/NuclearInteractionModel.inl

corsika/detail/modules/urqmd/UrQMD.inl

corsika/framework/process/ProcessSequence.hpp

corsika/modules/pythia8/Interaction.hpp

corsika/modules/qgsjetII/InteractionModel.hpp

corsika/modules/sibyll/InteractionModel.hpp

corsika/modules/sibyll/NuclearInteractionModel.hpp

corsika/modules/urqmd/UrQMD.hpp

examples/cascade_example.cpp

examples/corsika.cpp

examples/mars.cpp

examples/vertical_EAS.cpp

tests/modules/testPythia8.cpp

tests/modules/testQGSJetII.cpp

tests/modules/testSibyll.cpp