sops: fix compatibility with new format

The new format can have null values now.

pkgs/clan-cli/clan_cli/secrets/sops.py

@@ -449,15 +449,20 @@ def decrypt_file(secret_path: Path) -> str:
 
 def get_recipients(secret_path: Path) -> set[SopsKey]:
     sops_attrs = json.loads((secret_path / "secret").read_text())["sops"]
-    return {
+    keys = set()
+    for key_type in KeyType:
+        recipients = sops_attrs.get(key_type.name.lower())
+        if not recipients:
+            continue
+        for recipient in recipients:
+            keys.add(
                 SopsKey(
                     pubkey=recipient[key_type.sops_recipient_attr],
                     username="",
                     key_type=key_type,
                 )
-        for key_type in KeyType
-        for recipient in sops_attrs[key_type.name.lower()] or []
-    }
+            )
+    return keys
 
 
 def get_meta(secret_path: Path) -> dict: