Fix #494 regression in #search_form_for
Fix #494 regression in #search_form_for

Following which we need to add a test to cover this, and then this
logic might better be extracted out to separate methods or a PORO.

reinteractive/ransack,Eric-Guo/ransack,AndrewSwerlick/ransack,nagyt234/ransack,mariorcardoso/ransack,outstand/ransack,laserlemon/ransack,Mario245/ransack,roman-franko/ransack,martndemus/ransack,guilleva/ransack,vaski/ransack,johan--/ransack,activerecord-hackery/ransack,avit/ransack