Invalid MpdTpcDigit branch in root files

Branch MpdTpcDigit inside root files created, e.g., by reco.C can't be read using TBrowser in root. To demonstrate this, download attached mpddst files, open them inside root via TBrowser, enter branch mpdsim->MpdTpcDigit and try to doubleclick on any leaf. Program will crash (on mpddst_bad.root) with some kind of segfault error. Observations:

1. If right after (clean) start of root is opened via TBrowser file mpddst_bad.root and any of the mpdsim->MpdTpcDigit leaves are clicked, root crashes.
2. If after start of root is first loaded file mpddst_good.root some of the leaves are clicked and only afterwards (in the same root run) leaves of mpddst_bad.root are clicked, then everything works OK.
3. This does not affect only reading root files via TBrowser but also from external program as well (program gives non-descriptive segfault).
4. This regression was introduced with commit a0ff7d7b
5. Both files were created in the appropriate commits by the attached files runMC.C and reco.C.

mpddst_bad.root

mpddst_good.root

reco.C

runMC.C