diff --git a/erpnext/patches.txt b/erpnext/patches.txt
index 95d93853ad..57b75996c4 100644
--- a/erpnext/patches.txt
+++ b/erpnext/patches.txt
@@ -39,3 +39,4 @@ execute:frappe.db.sql("update `tabJournal Voucher` set voucher_type='Journal Ent
 execute:frappe.delete_doc("DocType", "Grade")
 erpnext.patches.4_0.remove_india_specific_fields
 execute:frappe.delete_doc_if_exists("DocType", "Warehouse User")
+execute:frappe.db.sql("delete from `tabWebsite Item Group` where ifnull(item_group, '')=''")
diff --git a/erpnext/stock/doctype/item/item.py b/erpnext/stock/doctype/item/item.py
index c4ca77fff2..9b2d8623b5 100644
--- a/erpnext/stock/doctype/item/item.py
+++ b/erpnext/stock/doctype/item/item.py
@@ -348,4 +348,5 @@ def get_last_purchase_details(item_code, doc_name=None, conversion_rate=1.0):
 def invalidate_cache_for_item(doc):
 	invalidate_cache_for(doc, doc.item_group)
 	for d in doc.get({"doctype":"Website Item Group"}):
-		invalidate_cache_for(doc, d.item_group)
+		if d.item_group:
+			invalidate_cache_for(doc, d.item_group)