500 error on creating invoice

When creating an invoice the pop-up does not disappears and I get the following error (in console):

VM1238:18 POST https://myurl.com/index.php/invoices/ajax/create 500 ();

In the debug log I see the follow error:

DEBUG - 2016-12-22 10:56:44 --> DB Transaction Failure
ERROR - 2016-12-22 10:56:44 --> Query error: Incorrect integer value: ‘’ for column ‘include_item_tax’ at row 1
DEBUG - 2016-12-22 10:56:44 --> Language file loaded: language/english/db_lang.php

When I refresh the page the concept invoice is there.

I run InvoicePlane on Nginx and PHP7 with SSL.

Any suggestions how to fix this issue?

I think I found the solution. InvoicePlane was written for older versions of MySQL so I had to disable Strict SQL mode in MySQL. See for more information: https://serverpilot.io/community/articles/how-to-disable-strict-mode-in-mysql-5-7.html