Fix edge cases: MQTT backwrite while first initializing is not complete

This PR improves/fixes edge cases where there is a: * backwrite from HA to MQTT before the first initialistation has been completed, * or initialisation has been completed but the Solmate did not send a proper response for boost or injection during the regular query The variables used are then not properly setup for further processing and cause a hard error. The solution was to check the variable state, log the cause and return, waiting for the next round. Note, if the Solmate continuosly refuses to send responses for the two variables in question, consecutive log entries are printed and no backwrite from HA via MQTT can be processed - until a response is received.