[FIX] web: on SearchPopup creation concat build context even if we have initial_ids
On SearchPopupCreation, if we have initial_ids - 1st search_read() will be
missing custom context defined on the field.
1. defined view like this: <field name='my_many2one_field_id' context="{'test': 1}"/>
2. in we expand the list of available item, name_search() has 'test' in context
3. in we click on 'Search More', search_read() is missing 'test' in context
4. if we change filter add/remove item, search_read() will have 'test' in context
Step 3. is wrong, should also have 'test' in context