Don't show restart prompt when changing folder label (fixes #2840)

lib/config/config.go

@@ -209,10 +209,14 @@ func (cfg *Configuration) prepare(myID protocol.DeviceID) {
 	// Ensure that any loose devices are not present in the wrong places
 	// Ensure that there are no duplicate devices
 	// Ensure that puller settings are sane
+	// Ensure that the versioning configuration parameter map is not nil
 	for i := range cfg.Folders {
 		cfg.Folders[i].Devices = ensureDevicePresent(cfg.Folders[i].Devices, myID)
 		cfg.Folders[i].Devices = ensureExistingDevices(cfg.Folders[i].Devices, existingDevices)
 		cfg.Folders[i].Devices = ensureNoDuplicateFolderDevices(cfg.Folders[i].Devices)
+		if cfg.Folders[i].Versioning.Params == nil {
+			cfg.Folders[i].Versioning.Params = map[string]string{}
+		}
 		sort.Sort(FolderDeviceConfigurationList(cfg.Folders[i].Devices))
 	}
 

lib/model/model.go

@@ -1942,9 +1942,11 @@ func (m *Model) CommitConfiguration(from, to config.Configuration) bool {
 			}
 		}
 
-		// Check if anything else differs, apart from the device list.
+		// Check if anything else differs, apart from the device list and label.
 		fromCfg.Devices = nil
 		toCfg.Devices = nil
+		fromCfg.Label = ""
+		toCfg.Label = ""
 		if !reflect.DeepEqual(fromCfg, toCfg) {
 			l.Debugln(m, "requires restart, folder", folderID, "configuration differs")
 			return false