container/autoroot: filter dentry with empty name

This is unreachable, but nice to have just in case.

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/autoroot.go

@@ -89,6 +89,8 @@ func IsAutoRootBindable(name string) bool {
 	case "mnt":
 	case "etc":
 
+	case "": // guard against accidentally binding /
+
 	default:
 		return true
 	}