fix: _rpc_list_custom_data send custom-data for all trades if a key is provided

freqtrade/rpc/rpc.py

@@ -1137,7 +1137,7 @@ class RPC:
             if key:
                 data = trade.get_custom_data(key=key)
                 if data:
-                    custom_data = [data]
+                    custom_data.append(data)
             else:
                 custom_data.extend(trade.get_all_custom_data())