made getters non nullable and removed all null assertion operators

lib/presentation/views/main_menu/group_view/create_group_view.dart

@@ -45,7 +45,7 @@ class _CreateGroupViewState extends State<CreateGroupView> {
         backgroundColor: CustomTheme.backgroundColor,
         scrolledUnderElevation: 0,
         title: Text(
-          AppLocalizations.of(context)!.create_new_group,
+          AppLocalizations.of(context).create_new_group,
           style: const TextStyle(fontSize: 20, fontWeight: FontWeight.bold),
         ),
         centerTitle: true,
@@ -58,7 +58,7 @@ class _CreateGroupViewState extends State<CreateGroupView> {
               margin: const EdgeInsets.symmetric(horizontal: 12, vertical: 10),
               child: TextInputField(
                 controller: _groupNameController,
-                hintText: AppLocalizations.of(context)!.group_name,
+                hintText: AppLocalizations.of(context).group_name,
                 onChanged: (value) {
                   setState(() {});
                 },
@@ -74,7 +74,7 @@ class _CreateGroupViewState extends State<CreateGroupView> {
               ),
             ),
             CustomWidthButton(
-              text: AppLocalizations.of(context)!.create_group,
+              text: AppLocalizations.of(context).create_group,
               sizeRelativeToWidth: 0.95,
               buttonType: ButtonType.primary,
               onPressed:

lib/presentation/views/main_menu/group_view/groups_view.dart

@@ -53,8 +53,8 @@ class _GroupsViewState extends State<GroupsView> {
               replacement: Center(
                 child: TopCenteredMessage(
                   icon: Icons.info,
-                  title: AppLocalizations.of(context)!.info,
-                  message: AppLocalizations.of(context)!.no_groups_created_yet,
+                  title: AppLocalizations.of(context).info,
+                  message: AppLocalizations.of(context).no_groups_created_yet,
                 ),
               ),
               child: ListView.builder(
@@ -74,7 +74,7 @@ class _GroupsViewState extends State<GroupsView> {
           Positioned(
             bottom: MediaQuery.paddingOf(context).bottom,
             child: CustomWidthButton(
-              text: AppLocalizations.of(context)!.create_group,
+              text: AppLocalizations.of(context).create_group,
               sizeRelativeToWidth: 0.90,
               onPressed: () async {
                 await Navigator.push(