Before this commit, when the portal user is in `/my/tasks` route
and he remove the groupby and search a certain task name and no
task is found with his search, a traceback is occurred saying `task`
is not found to be able to evaluate the following lines:
```xml
<t t-set="timesheet_ids" t-value="task.sudo().timesheet_ids"/>
<t t-set="is_uom_day" t-value="timesheet_ids._is_timesheet_encode_uom_day()"/>```
in the portal template.
This commit fixes the issue by changing the xpath to be sure the task
variable is defined before evaluating task.sudo().timesheet_ids.
Moreover, this commit checks if there is any task in tasks before
displaying tbody to avoid having any scrollbar for nothing.
task-2987387
X-original-commit: 9d0b770aebaf3c9c08352bf11fb9fdf2a36f1523
Part-of: odoo/odoo#104259
Pratik Awasthi
a95a848e06