Before this commit, the default picture (when no picture is set to a product) has been
changed for `product.template` but not for `product.product` in commit 0625434
This commit also applies the changes in `product.product` to have the same default
picture than `product.template` when there is no picture set on the product.
task-3484150
closes odoo/odoo#145831
X-original-commit: 40ee98e7b96bbd7d92f1bc085389e98fb43fd8d1
Signed-off-by: Xavier Bol (xbo) <xbo@odoo.com>