fix(ur): actually send usage report directly when enabled (#9736)

There was a bug that the unique ID was not set when reporting was
enabled, and thus the reports where rejected by the server. The unique
ID got set only on startup, so next time Syncthing restarted.

This makes sure to set the unique ID when blank.

lib/syncthing/syncthing.go

@@ -36,7 +36,6 @@ import (
 	"github.com/syncthing/syncthing/lib/model"
 	"github.com/syncthing/syncthing/lib/osutil"
 	"github.com/syncthing/syncthing/lib/protocol"
-	"github.com/syncthing/syncthing/lib/rand"
 	"github.com/syncthing/syncthing/lib/svcutil"
 	"github.com/syncthing/syncthing/lib/tlsutil"
 	"github.com/syncthing/syncthing/lib/upgrade"
@@ -291,11 +290,6 @@ func (a *App) startup() error {
 				// Unique ID will be set and config saved below if necessary.
 			}
 		}
-
-		// If we are going to do usage reporting, ensure we have a valid unique ID.
-		if cfg.Options.URAccepted > 0 && cfg.Options.URUniqueID == "" {
-			cfg.Options.URUniqueID = rand.String(8)
-		}
 	})
 
 	usageReportingSvc := ur.New(a.cfg, m, connectionsService, a.opts.NoUpgrade)