solved issue when no custom variable

src/meshcore/reader.py

@@ -205,6 +205,7 @@ class MessageReader:
             logger.debug(f"received custom vars response: {data.hex()}")
             res = {}
             rawdata = data[1:].decode()
+            if not rawdata == "" :
                 pairs = rawdata.split(",")
                 for p in pairs :
                     psplit = p.split(":")