4.1.5

@jpivarski fixed another Uproot-writing bug: writing TTrees didn't update the FreeSegments record, which means that writing another TTree (with another file handle, with uproot.update or ROOT) could overwrite the first TTree.

Like 4.1.4, this is an important bug-fix for anyone creating a robust dataset of ROOT files. (It doesn't affect you if you consider all files to be write-once only, but if you're ever thinking of updating files, this will matter. And besides, correctness is important in principle!)