diff -r 454ff0629121 account.py
--- a/trytond/trytond/modules/account_invoice/account.py	Tue Nov 08 18:47:58 2016 +0100
+++ b/trytond/trytond/modules/account_invoice/account.py	Sat Dec 03 08:10:22 2016 +0100
@@ -323,7 +323,8 @@
                 ('move', 'in', list(move_ids)),
                 ('account', 'in', list(account_ids)),
                 ])
-        Invoice.process(invoices)
+        if invoices:
+            Invoice.process(invoices)
         return reconciliations
 
     @classmethod
@@ -335,4 +336,5 @@
                 ('move', 'in', list(move_ids)),
                 ])
         super(Reconciliation, cls).delete(reconciliations)
-        Invoice.process(invoices)
+        if invoices:
+            Invoice.process(invoices)