syz-ci: fix null dereference when JobManager creation fails, skip when no dashboard

When starting syz-ci, if instantiating the JobManager fails (due to
dashapi.New() returning an error), we log an error and then proceed to go
right ahead and call the startLoop() method with a nil pointer anyway.

Fix this by only calling startLoop() if newJobManager() succeeded.

Additionally, one reason why setting up the JobManager might fail is when
you don't specify a dashboard address, which is an optional field in the
syz-ci config. There's no point having a JobManager without a dashboard,
so just skip this completely when there's no dashboard.

Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>

Author: ajdlinux

syz-ci/syz-ci.go

@@ -321,13 +321,17 @@ func main() {
 			}()
 		}
 	}
-	jm, err := newJobManager(cfg, managers, shutdownPending)
-	if err != nil {
-		log.Fatalf("failed to create dashapi connection %v", err)
-	}
+
 	ctxJobs, stopJobs := context.WithCancel(ctx)
 	wgJobs := sync.WaitGroup{}
-	jm.startLoop(ctxJobs, &wgJobs)
+	if cfg.DashboardAddr != "" {
+		jm, err := newJobManager(cfg, managers, shutdownPending)
+		if err != nil {
+			log.Fatalf("failed to create dashapi connection %v", err)
+		} else {
+			jm.startLoop(ctxJobs, &wgJobs)
+		}
+	}
 
 	// For testing. Racy. Use with care.
 	http.HandleFunc("/upload_cover", func(w http.ResponseWriter, r *http.Request) {