B #5040: Fix posible segfault in LogDB::purge_log (#157)
B #5040: Fix posible segfault in LogDB::purge_log (#157)

(cherry picked from commit fb0d1bb9066c5587b11a14d0b1e58caa5e7d96e8)

OpenNebula/one,OpenNebula/one,OpenNebula/one,OpenNebula/one,OpenNebula/one,OpenNebula/one,OpenNebula/one,OpenNebula/one,OpenNebula/one