treewide: fix modules options types where the default is null

They can be caught with `nixos-option -r` on an empty ({...}:{}) NixOS
configuration.

1 files changed, 1 insertions, 1 deletions

diff --git a/nixos/modules/services/misc/gammu-smsd.nix b/nixos/modules/services/misc/gammu-smsd.nix
index 3057d7fd1a0..552725f1384 100644
--- a/nixos/modules/services/misc/gammu-smsd.nix
+++ b/nixos/modules/services/misc/gammu-smsd.nix
@@ -172,7 +172,7 @@ in {
           };
 
           database = mkOption {
-            type = types.str;
+            type = types.nullOr types.str;
             default = null;
             description = "Database name to store sms data";
           };