Fix product_by_location with stock_skip_warehouse and no product_ids

issue3843
review5171002
(grafted from f2f79e388f07fede7be1273ad1e64477a78eaadf)

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branch : 2.6
extra : source : f2f79e388f07fede7be1273ad1e64477a78eaadf
extra : amend_source : e5926cd650e3a9a52f7dd5a99b2d45d25421a206
Prepare release 2.6.7

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branch : 2.6
Added tag 2.6.7 for changeset 6e0f95c20b85

--HG--
branch : 2.6
Increase version number

--HG--
branch : 2.6