prevent `nil` from being put back to `c.Container`
prevent `nil` from being put back to `c.Container`

`c.Exists()` is an innocent looking function being in fact a mutating operation: `c.Container` may be `nil` before and hold a looked up value after the call.

1yvT0s/os,duguhaotian/os,OnePaaS/os,rancherio/os,duguhaotian/os,duguhaotian/os,datawolf/os,rowhit/os,maxfierke/rancher-os,fentas/os,juliengk/os,rowhit/os,gpndata/os,1yvT0s/os,luxas/os,SvenDowideit/os,maxfierke/rancher-os,imikushin/os,imikushin/os,OnePaaS/os,fentas/os,ibuildthecloud/os,rowhit/os,1yvT0s/os,hairyhenderson/rancheros,datawolf/os,luxas/os,rancher/os,SvenDowideit/os,maxfierke/rancher-os,gizmotronic/os,gizmotronic/os,rancherio/os,OnePaaS/os,rancherio/os,luxas/os,hairyhenderson/rancheros,juliengk/os,gpndata/os,hairyhenderson/rancheros,rancher/os,fentas/os,ibuildthecloud/os,datawolf/os,gpndata/os