[heatpump] missing param last_update

pyheatpump/heatpump.py

@@ -10,7 +10,7 @@ from pyheatpump.models import *
 def get_variable_values(request):
     res = {}
     if 'time' not in request.path_params.keys():
-        h = Heatpump(config.get('heatpump', 'mac_address'))
+        h = Heatpump(config.get('heatpump', 'mac_address'), None)
     else:
         time = datetime.fromisoformat(request.params['time'])
         h = Heatpump(config.get('heatpump', 'mac_address'), request.params['time'])