AppPriority is an optional parameter.

We were incorrectly requiring its presence and logging an error when it
wasn't found.  The parameter was not intended to be mandatory and no
error should be logged unless the parameter is present but invalid.

registry.cpp

@@ -496,7 +496,7 @@ int get_parameters(nssm_service_t *service, STARTUPINFO *si) {
 
   /* Try to get priority - may fail. */
   unsigned long priority;
-  if (get_number(key, NSSM_REG_PRIORITY, &priority) == 1) {
+  if (get_number(key, NSSM_REG_PRIORITY, &priority, false) == 1) {
     if (priority == (priority & priority_mask())) service->priority = priority;
     else log_event(EVENTLOG_WARNING_TYPE, NSSM_EVENT_BOGUS_PRIORITY, service->name, NSSM_REG_PRIORITY, 0);
   }