Fix interoperability with pninexus.h5cpp
Without this fix, importing pninexus.h5cpp after asapo_producer crashed the interpreter with a std::bad_cast exception, cf. https://stackoverflow.com/questions/3765669 and commit 9bee6cd6
Without this fix, importing pninexus.h5cpp after asapo_producer crashed the interpreter with a std::bad_cast exception, cf. https://stackoverflow.com/questions/3765669 and commit 9bee6cd6