raftstore/region_info_accessor: Fix the panic when got overlapping regions with version 0 (#4030)
raftstore/region_info_accessor: Fix the panic when got overlapping regions with version 0 (#4030)

Signed-off-by: Connor <f7e3376ac32ecd54ff96995c24a9472cac06d4cb@gmail.com>
BusyJay/tikv,BusyJay/tikv,BusyJay/tikv,c4pt0r/tikv,pingcap/tikv,pingcap/tikv,BusyJay/tikv