Fix panic when receiving a config to update to if some settings are not set (#13889)

api4/config.go

@@ -57,6 +57,8 @@ func updateConfig(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	cfg.SetDefaults()
+
 	if !c.App.SessionHasPermissionTo(*c.App.Session(), model.PERMISSION_MANAGE_SYSTEM) {
 		c.SetPermissionError(model.PERMISSION_MANAGE_SYSTEM)
 		return