fix: fail migration due to None type during v13_0.update_returned_qty…

…_in_pr_dn (frappe#27430)

* fix: fail migration due to None type

* fix: incorrect key: value pair in filter.

Co-authored-by: Ankush Menat <ankush@iwebnotes.com>

erpnext/patches/v13_0/update_returned_qty_in_pr_dn.py

@@ -13,7 +13,7 @@ def execute():
 	frappe.reload_doc('stock', 'doctype', 'stock_settings')
 
 	def update_from_return_docs(doctype):
-		for return_doc in frappe.get_all(doctype, filters={'is_return' : 1, 'docstatus' : 1}):
+		for return_doc in frappe.get_all(doctype, filters={'is_return' : 1, 'docstatus' : 1, 'return_against': ('!=', '')}):
 			# Update original receipt/delivery document from return
 			return_doc = frappe.get_cached_doc(doctype, return_doc.name)
 			try: