An X2many always has at least 4 lines. If the X2many contains less
than 4 filled lines (Record or "Add a line") empty lines are added
to make up the difference.
For example, an X2many in edit mode containing only one record:
- Line containing a record
- Line containing "Add a line
- Empty line
- Empty line
closesodoo/odoo#97070
Signed-off-by: Aaron Bohy (aab) <aab@odoo.com>