just checking whether m is not NULL (get_diff sometimes throw config_not_set
just checking whether m is not NULL (get_diff sometimes throw config_not_set

kmaehashi/jubatus_core,jubatus/jubatus,kmaehashi/jubatus_core,rimms/jubatus_core,elkingtonmcb/jubatus,jubatus/jubatus,rimms/jubatus_core,kumagi/jubatus_core,kmaehashi/jubatus_core,gintenlabo/jubatus_core,kumagi/jubatus_core,Asuka52/jubatus,kumagi/jubatus_core,gintenlabo/jubatus,rimms/jubatus,elkingtonmcb/jubatus,gintenlabo/jubatus,rimms/jubatus_core,mathn/jubatus,mathn/jubatus,gintenlabo/jubatus_core,gintenlabo/jubatus_core,roselleebarle04/jubatus,roselleebarle04/jubatus,jubatus/jubatus,rimms/jubatus,gintenlabo/jubatus_core,rimms/jubatus_core,Asuka52/jubatus,kumagi/jubatus_core,kmaehashi/jubatus,kmaehashi/jubatus_core,kmaehashi/jubatus