Do not use supplier location if empty

issue10240
review350071002
(grafted from 9d974b18ef9d11a7f4a62c044d4f1110d39f559c)

--HG--
branch : 6.0

purchase.py

@@ -1433,7 +1433,8 @@ class Line(sequence_ordered(), ModelSQL, ModelView):
 
     def get_from_location(self, name):
         if (self.quantity or 0) >= 0:
-            return self.purchase.party.supplier_location.id
+            if self.purchase.party.supplier_location:
+                return self.purchase.party.supplier_location.id
         elif self.purchase.return_from_location:
             return self.purchase.return_from_location.id
 
@@ -1441,7 +1442,7 @@ class Line(sequence_ordered(), ModelSQL, ModelView):
         if (self.quantity or 0) >= 0:
             if self.purchase.warehouse:
                 return self.purchase.warehouse.input_location.id
-        else:
+        elif self.purchase.party.supplier_location:
             return self.purchase.party.supplier_location.id
 
     @fields.depends('moves', methods=['planned_delivery_date'])