MM-27178: Use FileSettings.Directory in export tool (#15100)

* MM-27178: use FileSettings.Directory in export

* Set empty FileSettings.Directory to default value

* Validate that FileSettings.Directory is non-empty

* Don't set FileSettings.Directory to / in fixConfig

* Run make i18n-extract

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

config/utils.go

@@ -67,7 +67,7 @@ func fixConfig(cfg *model.Config) bool {
 
 	// Ensure the directory for a local file store has a trailing slash.
 	if *cfg.FileSettings.DriverName == model.IMAGE_DRIVER_LOCAL {
-		if !strings.HasSuffix(*cfg.FileSettings.Directory, "/") {
+		if *cfg.FileSettings.Directory != "" && !strings.HasSuffix(*cfg.FileSettings.Directory, "/") {
 			*cfg.FileSettings.Directory += "/"
 			changed = true
 		}