avoid errors during authentication

we may not have a fully initialized protocol object yet

xpra/client/base/client_base.py

@@ -1034,6 +1034,8 @@ def get_encryption(self) -> str:
         if not p:
             return ""
         conn = p._conn
+        if not conn:
+            return ""
         #prefer the socket option, fallback to "--encryption=" option:
         encryption = conn.options.get("encryption", self.encryption)
         cryptolog(f"get_encryption() connection options encryption={encryption!r}")