[framework] Segfault when Edm4hepConverter created in initialize

[vvolkl]

See discussion in #23

[andresailer]

direct link to the discussion? #23 (comment)

[tmadlener]

The reason for the segmentation fault is that internally the converter holds a std::unordered_map<std::string, podio::CollectionBase*>. The converter assumes that something external takes owenership of these exactly once. This works in the standalone case, where the EventStore takes this role. In the framework case the DataHandle of the first event takes ownership, hence, on the second event the pointers are no longer accessible.

The underlying reason is fixed by #85. I will open a separate pull request making the actual changes to not instantiate the converter each event once that has been merged.