fixed error in receivable voucher (fetching pos warehosue)
diff --git a/accounts/doctype/receivable_voucher/receivable_voucher.py b/accounts/doctype/receivable_voucher/receivable_voucher.py
index 267ea92..f26374a 100644
--- a/accounts/doctype/receivable_voucher/receivable_voucher.py
+++ b/accounts/doctype/receivable_voucher/receivable_voucher.py
@@ -580,6 +580,7 @@
 	# Get Warehouse
 	def get_warehouse(self):
 		w = sql("select warehouse from `tabPOS Setting` where ifnull(user,'') = '%s' and company = '%s'" % (session['user'], self.doc.company))
+		w = w and w[0][0] or ''
 		if not w:
 			ps = sql("select name, warehouse from `tabPOS Setting` where ifnull(user,'') = '' and company = '%s'" % self.doc.company)
 			if not ps: