ensure manually entered date ranges are preserved in smart groups

[jmcclelland]

See https://lab.civicrm.org/dev/core/issues/396

Overview

Due to a regression introduced by #11486, smart groups based on manually entered date ranges fail to properly filter by the date ranges when executed.

Before

If you create a smart group based on a search using one of several specially identified date fields (including event participant registration date) and you manually specify a date range instead of selecting a pre-chosen range, then your smart group will be properly saved, but the date range will be ignored when the saved search is executed.

After

Smart groups based on manually selected date ranges properly select the right contacts based on the date ranges entered.

Technical Details

Prior to the fix, CiviCRM issued an undefined index error.

[eileenmcnaughton]

@jmcclelland this patch is good & test is super. I am closing this in favour of putting it against the rc - #12909