fix: type-cast while saving an item (backport #32549) (#32578)

fix: type-cast while saving an item (#32549)

(cherry picked from commit 43037d8)

Co-authored-by: Rohan <Alchez@users.noreply.github.com>

erpnext/stock/doctype/item/item.py

@@ -232,10 +232,10 @@ def validate_retain_sample(self):
 
 	def clear_retain_sample(self):
 		if not self.has_batch_no:
-			self.retain_sample = None
+			self.retain_sample = False
 
 		if not self.retain_sample:
-			self.sample_quantity = None
+			self.sample_quantity = 0
 
 	def add_default_uom_in_conversion_factor_table(self):
 		if not self.is_new() and self.has_value_changed("stock_uom"):

erpnext/stock/doctype/item/test_item.py

@@ -722,8 +722,8 @@ def test_retain_sample(self):
 
 		item.has_batch_no = None
 		item.save()
-		self.assertEqual(item.retain_sample, None)
-		self.assertEqual(item.sample_quantity, None)
+		self.assertEqual(item.retain_sample, False)
+		self.assertEqual(item.sample_quantity, 0)
 		item.delete()
 
 	def consume_item_code_with_differet_stock_transactions(