[FIX] - date_end required only for contract product

product_contract/views/sale_order.xml

@@ -55,7 +55,7 @@
                            attrs="{'required': [('is_contract', '=', True)]}"/>
                 </group>
                 <group attrs="{'invisible': [('is_contract', '=', False)]}">
-                    <field name="date_end" required="True"/>
+                    <field name="date_end" attrs="{'required': [('is_contract', '=', True)]}"/>
                 </group>
             </xpath>
             <xpath expr="//field[@name='order_line']/tree//field[@name='price_total']"