Admin order creation fails when "Include Tax In Order Total" set to yes

[erikhansen]

Steps to reproduce issue:

1. Install Magento CE 2.0.0 with sample data.
2. Ensure that developer mode is turned on.
3. Go to Stores > Configuration > SALES > Tax > Shopping Cart Display Settings and change the "Include Tax In Order Total" value to "Yes".
4. Go to Sales > Orders > Create New Order
5. You will see this error: Notice: Undefined index: tax in vendor/magento/module-sales/Block/Adminhtml/Order/Create/Totals/Grandtotal.php on line 77 Full backtrace available here

This problem occurs because the \Magento\Tax\Model\Sales\Total\Quote\Tax::collect collector only returns a value if there are items in a quote. And since the quote won't contain any items, the "tax" collector isn't present in the totals array. I'll be submitting a PR to fix this shortly.

[tang-yu]

This issue has been fixed in internal ticket MAGETWO-46808. Thanks for submitting the defect.