fix: repeating tasks don't update dates when moving in done bucket

pkg/models/kanban_task_bucket.go

@@ -23,6 +23,7 @@ import (
 	"code.vikunja.io/api/pkg/events"
 	"code.vikunja.io/api/pkg/user"
 	"code.vikunja.io/api/pkg/web"
+	"github.com/jinzhu/copier"
 	"xorm.io/xorm"
 )
 
@@ -157,7 +158,11 @@ func (b *TaskBucket) Update(s *xorm.Session, a web.Auth) (err error) {
 			doneChanged = true
 			task.Done = true
 			if task.isRepeating() {
-				oldTask := task
+				oldTask := &Task{}
+				err = copier.Copy(oldTask, task)
+				if err != nil {
+					return err
+				}
 				oldTask.Done = false
 				updateDone(oldTask, task)
 				updateBucket = false