Test from location when checking warehouse for purchase line with negative quantity

Closes #14333
(grafted from f21002c5cb1882a5cc6e7375aec7db45fc56698f)

--HG--
branch : 6.0

modules/purchase/purchase.py

@@ -745,7 +745,11 @@ class Purchase(
 
     def check_for_quotation(self):
         for line in self.lines:
-            if (not line.to_location
+            if (line.quantity or 0) >= 0:
+                location = line.to_location
+            else:
+                location = line.from_location
+            if (not location
                     and line.product
                     and line.product.type in ('goods', 'assets')):
                 raise PurchaseQuotationError(