nixos/opendkim: Fix CapabilityBoundingSet option

An empty list results in no CapabilityBoundingSet at all, an empty
string however will set `CapabilityBoundingSet=`, which represents a
closed set.

Related: #120617

Changed files
+1 -1
nixos
modules
services
+1 -1
nixos/modules/services/mail/opendkim.nix
···
ReadWritePaths = [ cfg.keyPath ];
AmbientCapabilities = [];
-
CapabilityBoundingSet = [];
DevicePolicy = "closed";
LockPersonality = true;
MemoryDenyWriteExecute = true;
···
ReadWritePaths = [ cfg.keyPath ];
AmbientCapabilities = [];
+
CapabilityBoundingSet = "";
DevicePolicy = "closed";
LockPersonality = true;
MemoryDenyWriteExecute = true;