make due date, invoice_portion mandatory
diff --git a/erpnext/controllers/accounts_controller.py b/erpnext/controllers/accounts_controller.py
index cc624c8..16b22ce 100644
--- a/erpnext/controllers/accounts_controller.py
+++ b/erpnext/controllers/accounts_controller.py
@@ -666,7 +666,7 @@
 	def validate_invoice_portion(self):
 		total_portion = 0
 		for term in self.payment_schedule:
-			total_portion += term.invoice_portion
+			total_portion += flt(term.get('invoice_portion', 0))
 
 		if flt(total_portion, 2) != 100.00:
 			frappe.msgprint(_('Combined invoice portion must equal 100%'), raise_exception=1, indicator='red')