Allow secrets to be missing

morph/grid/testing/grid.nix

@@ -6,7 +6,12 @@ import ../../lib/make-grid.nix {
   config = ./config.json;
   nodes = cfg:
   let
-    sshUsers = import ../../../../PrivateStorageSecrets/staging-users.nix;
+    importDef = default: path: (
+      if builtins.pathExists path
+      then import path
+      else default
+    );
+    sshUsers = importDef {} ../../../../PrivateStorageSecrets/staging-users.nix;
   in {
     "payments.privatestorage-staging.com" = import ../../lib/issuer.nix ({
       inherit sshUsers;