Fix panic if miss notification sock is nil
Fix panic if miss notification sock is nil

Signed-off-by: Jana Radhakrishnan <045898bda7d4800fe4909a9831e702ab79e266be@docker.com>

docker/docker,mahak/docker,trebonian/docker,yosifkit/docker,djs55/docker,jimjag/docker,trebonian/docker,Ramzec/docker,konstruktoid/docker-upstream,paralin/docker,flavio/docker,konstruktoid/docker-upstream,jameszhan/docker,gnailuy/docker,thaJeztah/docker,jimjag/docker,bearstech/moby,Mokolea/docker,djs55/docker,djs55/docker,jthelin/docker,cpuguy83/docker,paralin/docker,docker/docker,jimjag/docker,AkihiroSuda/docker,nalind/docker,yosifkit/docker,bearstech/moby,nawawi/docker,AkihiroSuda/docker,moby/moby,mahak/docker,konstruktoid/docker-upstream,nawawi/docker,Ramzec/docker,thaJeztah/docker,moul/docker,gnailuy/docker,Mokolea/docker,vdemeester/docker,flavio/docker,vdemeester/docker,Mokolea/docker,bearstech/moby,jthelin/docker,AkihiroSuda/docker,konstruktoid/docker-upstream,paralin/docker,moby/moby,gnailuy/docker,cpuguy83/docker,flavio/docker,cpuguy83/docker,yosifkit/docker,moul/docker,Mokolea/docker,jameszhan/docker,moby/moby,moul/docker,nalind/docker,trebonian/docker,paralin/docker,jameszhan/docker,bearstech/moby,jimjag/docker,AkihiroSuda/docker,yosifkit/docker,thaJeztah/docker,thaJeztah/docker,Ramzec/docker,Ramzec/docker,mahak/docker,cpuguy83/docker,nalind/docker,gnailuy/docker,docker/docker,trebonian/docker,nawawi/docker,vdemeester/docker,nawawi/docker,flavio/docker,mahak/docker,moby/moby,nalind/docker,moul/docker