My search query gives me an error

My search query gives me an error only when I try to submit an empty query.

search?query= 

If I search for anything it works fine

search?query=test

Where I can find this error I tried search.inc.php  still the same
It happened after the update to 2.1. I will have to restore and try again thanks TiM
I just download it and installed on my localhost and same error it is something with 2.1
Can you list your sql_modes? What database daemon and version is this? MySQL or MariaDB?
I use MySQL 5.6.35
MAMP and XAMPP everything is default and both give me the same error
I downloaded it directly from GitHub and it works now you already fixed it after releasing 2.1 version.
Then it's probably the regex when searching for code, sku, gtin or mpn. It will be official in a 2.1.1. The fix however conserned a different error message. Another topic on this forum.
Probably, It will be nice to fix search to show only one product on search result when we search by code, sku. 
Thanks