Ignore invalid companion auth shapes (#1405)

companion/pairing.py

@@ -64,11 +64,16 @@ def find_admin_user() -> str | None:
     auth_path = os.path.join("data", "auth.json")
     try:
         with open(auth_path, "r", encoding="utf-8") as f:
-            users = (json.load(f) or {}).get("users", {})
+            data = json.load(f)
     except (OSError, json.JSONDecodeError):
         return None
+    if not isinstance(data, dict):
+        return None
+    users = data.get("users") or {}
+    if not isinstance(users, dict):
+        return None
     for uname, udata in users.items():
-        if udata.get("is_admin") is True:
+        if isinstance(udata, dict) and udata.get("is_admin") is True:
             return uname
     return next(iter(users), None)