[fix] [minor] SO/DN required validation and get_single_value deprecated
diff --git a/accounts/doctype/purchase_invoice/purchase_invoice.py b/accounts/doctype/purchase_invoice/purchase_invoice.py
index 9e220fd..693ed84 100644
--- a/accounts/doctype/purchase_invoice/purchase_invoice.py
+++ b/accounts/doctype/purchase_invoice/purchase_invoice.py
@@ -252,14 +252,14 @@
 		self.doc.against_expense_account = ",".join(against_accounts)
 
 	def po_required(self):
-		if webnotes.conn.get_single_value("Buying Settings", "po_required") == 'Yes':
+		if webnotes.conn.get_value("Buying Settings", None, "po_required") == 'Yes':
 			 for d in getlist(self.doclist,'entries'):
 				 if not d.purchase_order:
 					 msgprint("Purchse Order No. required against item %s"%d.item_code)
 					 raise Exception
 
 	def pr_required(self):
-		if webnotes.conn.get_single_value("Buying Settings", "pr_required") == 'Yes':
+		if webnotes.conn.get_value("Buying Settings", None, "pr_required") == 'Yes':
 			 for d in getlist(self.doclist,'entries'):
 				 if not d.purchase_receipt:
 					 msgprint("Purchase Receipt No. required against item %s"%d.item_code)
diff --git a/accounts/doctype/sales_invoice/sales_invoice.py b/accounts/doctype/sales_invoice/sales_invoice.py
index 09df5f6..bf5e201 100644
--- a/accounts/doctype/sales_invoice/sales_invoice.py
+++ b/accounts/doctype/sales_invoice/sales_invoice.py
@@ -430,8 +430,8 @@
 	def so_dn_required(self):
 		"""check in manage account if sales order / delivery note required or not."""
 		dic = {'Sales Order':'so_required','Delivery Note':'dn_required'}
-		for i in dic:	
-			if webnotes.conn.get_single_value('Selling Settings', dic[i]) == 'Yes':
+		for i in dic:
+			if webnotes.conn.get_value('Selling Settings', None, dic[i]) == 'Yes':
 				for d in getlist(self.doclist,'entries'):
 					if webnotes.conn.get_value('Item', d.item_code, 'is_stock_item') == 'Yes' \
 						and not d.fields[i.lower().replace(' ','_')]:
diff --git a/stock/doctype/delivery_note/delivery_note.py b/stock/doctype/delivery_note/delivery_note.py
index 25a70b6..5df531e 100644
--- a/stock/doctype/delivery_note/delivery_note.py
+++ b/stock/doctype/delivery_note/delivery_note.py
@@ -85,7 +85,7 @@
 
 	def so_required(self):
 		"""check in manage account if sales order required or not"""
-		if webnotes.conn.get_single_value("Selling Settings", 'so_required') == 'Yes':
+		if webnotes.conn.get_value("Selling Settings", None, 'so_required') == 'Yes':
 			 for d in getlist(self.doclist,'delivery_note_details'):
 				 if not d.prevdoc_docname:
 					 msgprint("Sales Order No. required against item %s"%d.item_code)
diff --git a/stock/doctype/purchase_receipt/purchase_receipt.py b/stock/doctype/purchase_receipt/purchase_receipt.py
index 703929c..9daff8f 100644
--- a/stock/doctype/purchase_receipt/purchase_receipt.py
+++ b/stock/doctype/purchase_receipt/purchase_receipt.py
@@ -118,7 +118,7 @@
 			
 
 	def po_required(self):
-		if webnotes.conn.get_single_value("Buying Settings", "po_required") == 'Yes':
+		if webnotes.conn.get_value("Buying Settings", None, "po_required") == 'Yes':
 			 for d in getlist(self.doclist,'purchase_receipt_details'):
 				 if not d.prevdoc_docname:
 					 msgprint("Purchse Order No. required against item %s"%d.item_code)