[FIX] stock_account: prevent division by zero

In case of a move where source location = destination location, the result of
SUM(quantity) would be 0 and ending up with a division by zero.

Closes #12247
Closes #12423

addons/stock_account/wizard/stock_valuation_history.py

@@ -125,7 +125,7 @@ class stock_history(osv.osv):
                 product_categ_id,
                 SUM(quantity) as quantity,
                 date,
-                SUM(price_unit_on_quant * quantity) / SUM(quantity) as price_unit_on_quant,
+                COALESCE(SUM(price_unit_on_quant * quantity) / NULLIF(SUM(quantity), 0), 0) as price_unit_on_quant,
                 source
                 FROM
                 ((SELECT