Make dateTimeUtil null safe

lib/data/holidays.dart

@@ -1,20 +1,20 @@
 import 'package:photos/models/search/holiday_search_result.dart';
 
 const List<HolidayData> allHolidays = [
-  HolidayData('New Year', 1, 1),
-  HolidayData('Epiphany', 1, 6),
-  HolidayData('Pongal', 1, 14),
-  HolidayData('Makar Sankranthi', 1, 14),
-  HolidayData('Valentine\'s Day', 2, 14),
-  HolidayData('Nowruz', 3, 21),
-  HolidayData('Walpurgis Night', 4, 30),
-  HolidayData('Vappu', 4, 30),
-  HolidayData('May Day', 5, 1),
-  HolidayData('Midsummer\'s Eve', 6, 24),
-  HolidayData('Midsummer Day', 6, 25),
-  HolidayData('Christmas Eve', 12, 24),
-  HolidayData('Halloween', 10, 31),
-  HolidayData('Christmas', 12, 25),
-  HolidayData('Boxing Day', 12, 26),
-  HolidayData('New Year\'s Eve', 12, 31),
+  HolidayData('New Year', month: 1, day: 1),
+  HolidayData('Epiphany', month: 1, day: 6),
+  HolidayData('Pongal', month: 1, day: 14),
+  HolidayData('Makar Sankranthi', month: 1, day: 14),
+  HolidayData('Valentine\'s Day', month: 2, day: 14),
+  HolidayData('Nowruz', month: 3, day: 21),
+  HolidayData('Walpurgis Night', month: 4, day: 30),
+  HolidayData('Vappu', month: 4, day: 30),
+  HolidayData('May Day', month: 5, day: 1),
+  HolidayData('Midsummer\'s Eve', month: 6, day: 24),
+  HolidayData('Midsummer Day', month: 6, day: 25),
+  HolidayData('Christmas Eve', month: 12, day: 24),
+  HolidayData('Halloween', month: 10, day: 31),
+  HolidayData('Christmas', month: 12, day: 25),
+  HolidayData('Boxing Day', month: 12, day: 26),
+  HolidayData('New Year\'s Eve', month: 12, day: 31),
 ];

lib/models/search/holiday_search_result.dart

@@ -11,5 +11,5 @@ class HolidayData {
   final String name;
   final int month;
   final int day;
-  const HolidayData(this.name, this.month, this.day);
+  const HolidayData(this.name, {required this.month, required this.day});
 }

lib/utils/date_time_util.dart

@@ -1,5 +1,3 @@
-// @dart=2.9
-
 import 'package:flutter/material.dart';
 import 'package:intl/intl.dart';
 
@@ -52,32 +50,32 @@ String getMonthAndYear(DateTime dateTime) {
 
 //Thu, 30 Jun
 String getDayAndMonth(DateTime dateTime) {
-  return _days[dateTime.weekday] +
+  return _days[dateTime.weekday]! +
       ", " +
       dateTime.day.toString() +
       " " +
-      _months[dateTime.month];
+      _months[dateTime.month]!;
 }
 
 //30 Jun, 2022
 String getDateAndMonthAndYear(DateTime dateTime) {
   return dateTime.day.toString() +
       " " +
-      _months[dateTime.month] +
+      _months[dateTime.month]! +
       ", " +
       dateTime.year.toString();
 }
 
 String getDay(DateTime dateTime) {
-  return _days[dateTime.weekday];
+  return _days[dateTime.weekday]!;
 }
 
 String getMonth(DateTime dateTime) {
-  return _months[dateTime.month];
+  return _months[dateTime.month]!;
 }
 
 String getFullMonth(DateTime dateTime) {
-  return _fullMonths[dateTime.month];
+  return _fullMonths[dateTime.month]!;
 }
 
 String getAbbreviationOfYear(DateTime dateTime) {
@@ -201,7 +199,7 @@ Widget getDayWidget(
       getDayTitle(timestamp),
       style: (getDayTitle(timestamp) == "Today" && !smallerTodayFont)
           ? Theme.of(context).textTheme.headline5
-          : Theme.of(context).textTheme.caption.copyWith(
+          : Theme.of(context).textTheme.caption?.copyWith(
                 fontSize: 16,
                 fontWeight: FontWeight.w600,
                 fontFamily: 'Inter-SemiBold',
@@ -232,7 +230,8 @@ String secondsToHHMMSS(int value) {
   h = value ~/ 3600;
   m = ((value - h * 3600)) ~/ 60;
   s = value - (h * 3600) - (m * 60);
-  final String hourLeft = h.toString().length < 2 ? "0" + h.toString() : h.toString();
+  final String hourLeft =
+      h.toString().length < 2 ? "0" + h.toString() : h.toString();
 
   final String minuteLeft =
       m.toString().length < 2 ? "0" + m.toString() : m.toString();