fix rare crash in forkcontext
fix rare crash in forkcontext

biddyweb/flexisip,gale320/flexisip,BelledonneCommunications/flexisip,gale320/flexisip,gale320/flexisip,BelledonneCommunications/flexisip,BelledonneCommunications/flexisip,biddyweb/flexisip,biddyweb/flexisip,gale320/flexisip,BelledonneCommunications/flexisip,biddyweb/flexisip