Null pointer exception when config to region CN470

[womeikong]

RegionCN470.c, line 400 : A null pointer exception occurred when struct ChannelPlanCtx used without initialization in RegionCN470GetPhyParam function.
I think RegionInitDefaults function should be called at the beginning of LoRaMacInitialization function of LoRaMac.c to initialize struct ChannelPlanCtx first with all function pointers.

Gary Yang