[imp]web_tip : added condition to avoid tip if element on which tip is g...

...oing to display is hidden

- Task: https://www.odoo.com/web#id=10119&view_type=form&model=project.task&menu_id=3942&action=327
- Pad: https://pad.odoo.com/p/r.zEyS3rsk8LcavM52