Adds a check if the vertex exists before adding attributes in ReaderHepMC2
- Adds a check if the vertex exists before adding attributes in ReaderHepMC2. The vertex might be deleted higher in the code if it has no incoming/outgoing particles, see "Remove vertices with no incoming particles or no outgoing particles".
- Add a test Closes #107 (closed)
Edited by Andrii Verbytskyi