diff --git a/erpnext/controllers/queries.py b/erpnext/controllers/queries.py
index 4a30eed..d555532 100644
--- a/erpnext/controllers/queries.py
+++ b/erpnext/controllers/queries.py
@@ -200,7 +200,7 @@
 
 def get_project_name(doctype, txt, searchfield, start, page_len, filters):
 	cond = ''
-	if filters['customer']:
+	if filters.get('customer'):
 		cond = '(`tabProject`.customer = "' + filters['customer'] + '" or ifnull(`tabProject`.customer,"")="") and'
 
 	return frappe.db.sql("""select `tabProject`.name from `tabProject`
diff --git a/erpnext/support/doctype/maintenance_schedule/maintenance_schedule.py b/erpnext/support/doctype/maintenance_schedule/maintenance_schedule.py
index f276b56..4b06fe0 100644
--- a/erpnext/support/doctype/maintenance_schedule/maintenance_schedule.py
+++ b/erpnext/support/doctype/maintenance_schedule/maintenance_schedule.py
@@ -194,6 +194,9 @@
 			sr_details = frappe.db.get_value("Serial No", serial_no,
 				["warranty_expiry_date", "amc_expiry_date", "status", "delivery_date"], as_dict=1)
 
+			if not sr_details:
+				frappe.throw(_("Serial No {0} not found").format(serial_no))
+
 			if sr_details.warranty_expiry_date and sr_details.warranty_expiry_date>=amc_start_date:
 				throw(_("Serial No {0} is under warranty upto {1}").format(serial_no, sr_details.warranty_expiry_date))