fix compilation error

Author: matth-x

platformio.ini

@@ -40,7 +40,7 @@ lib_deps =
   jeremypoulter/[email protected]
   #matth-x/[email protected]
   #matth-x/[email protected]
-  https://github.com/matth-x/MicroOcpp#a36e6a443fe660f27b8b21eceb55db5b59e5c3b2
+  https://github.com/matth-x/MicroOcpp#c9d098efea03fcdaa3b036999df586d00a96c0be
   https://github.com/matth-x/MicroOcppMongoose#d83b081e0db377ec874d34ff6095812204e25b6f
 lib_ignore = WebSockets ; MicroOcpp: don't compile built-in WS library
 extra_scripts =