If somehow there is no selection but the `_handleShortcuts` handler still gets
called with `CTRL+A`, `container` would be a JQUERY object instead of an
element leading to a crash in `selectNodeContents` which expects a `Node`.

task-3506666

closes odoo/odoo#136319

X-original-commit: 4feaca67
Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>
Signed-off-by: Damien Abeloos (abd) <abd@odoo.com>