Update the start index of the for loop.

Previously the open date was never acted on, and so the for loop started
at one which skipped the open date.  Now it needs to be acted on.

htdocs/js/DatePicker/datepicker.js

@@ -55,7 +55,7 @@
 				groupRules[activeIndex][0]?.parentNode._flatpickr.selectedDates[0]?.getTime() ||
 				groupRules[activeIndex][1];
 
-			for (let i = 1; i < groupRules.length; ++i) {
+			for (let i = 0; i < groupRules.length; ++i) {
 				if (i == activeFieldDate) continue;
 				const thisFieldDate =
 					groupRules[i][0]?.parentNode._flatpickr.selectedDates[0]?.getTime() || groupRules[i][1];