pkg/apiserver: fix scenario count in debug log (#4333)

i.e.
DEBU[2026-02-18T12:34:31+01:00] 1 scenarios for machine 1
DEBU[2026-02-18T12:34:31+01:00] Returning list of scenarios : []

Author: mmetc

pkg/apiserver/apic.go

@@ -94,8 +94,14 @@ func (a *apic) FetchScenariosListFromDB(ctx context.Context) ([]string, error) {
 	if err != nil {
 		return nil, fmt.Errorf("while listing machines: %w", err)
 	}
+
 	// merge all scenarios together
 	for _, v := range machines {
+		if v.Scenarios == "" {
+			log.Debugf("No scenarios for machine %d", v.ID)
+			continue
+		}
+
 		machineScenarios := strings.Split(v.Scenarios, ",")
 		log.Debugf("%d scenarios for machine %d", len(machineScenarios), v.ID)