fix: don't panic when test cannot start

cluster_test.go

@@ -82,9 +82,11 @@ func (s *clusterScenario) newClusterClient(
 
 func (s *clusterScenario) Close() error {
 	for _, port := range s.ports {
-		processes[port].Close()
+		if process, ok := processes[port]; ok {
+			process.Close()
 			delete(processes, port)
 		}
+	}
 	return nil
 }