Hi all 
i am currently migrating a shop from M1.7.0.2 to M2.
I already did it successfully on 2.1 some months ago, using the map.xml´s and ignoring all unkonwn fields. On Magento 2.2 i am now using the -a (auto) option for ignoring these fields.
its running almost perfect and all data is available like customers, oders etc..., but i got only one problem. the page of /customer/account/create is throwing an exception which says nothing to me:
Exception #0 (Exception): Warning: A non-numeric value encountered in /var/www/magento2/vendor/magento/zendframework1/library/Zend/Locale/Math/PhpMath.php on line 94
You can see the complete message here:
http://euve258246.serverprofi24.de/customer/account/create/
Note, that creating a user in the checkout is working correctly. And like i said, the problem did not occour when i was migrating to magento 2.1.
php is 7.1.11:
PHP 7.1.11-1+ubuntu16.04.1+deb.sury.org+1 (cli) (built: Oct 27 2017 13:49:56) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.1.0, Copyright (c) 1998-2017 Zend Technologies
with Zend OPcache v7.1.11-1+ubuntu16.04.1+deb.sury.org+1, Copyright (c) 1999-2017, by Zend Technologies
hoping for some good idea
thank you!