fix(server): Clean up a clang analyzer warning in ua_subscription_monitoreditem.c
fix(server): Clean up a clang analyzer warning in ua_subscription_monitoreditem.c

jpfr/open62541,JGrothoff/open62541,JGrothoff/open62541,jpfr/open62541,JGrothoff/open62541,open62541/open62541,JGrothoff/open62541,open62541/open62541,jpfr/open62541,open62541/open62541,jpfr/open62541,open62541/open62541