Fix all warnings

lib/ui/widgets/account_image_widget.dart

@@ -23,7 +23,7 @@ class AccountImageWidget extends StatelessWidget {
   Widget build(BuildContext context) {
     return Material(
       child: CachedNetworkImage(
-        imageUrl: user.accountImageURL!,
+        imageUrl: user.accountImageURL,
         width: width,
         height: width,
         fit: BoxFit.cover,

lib/ui/widgets/mobile_mode/mobile_appbar_widget.dart

@@ -217,6 +217,8 @@ class _ComunicMobileAppBarState extends SafeState<ComunicMobileAppBar> {
       case BarCallbackActions.ACTION_LOGOUT:
         controller!.requestLogout();
         break;
+      default:
+        break;
     }
   }
 }

lib/ui/widgets/tablet_mode/global_search_field.dart

@@ -169,7 +169,7 @@ class _SearchResultsWidget extends StatelessWidget {
           leading: AccountImageWidget(user: user),
           title: Text(user.displayName),
           onTap: () {
-            MainController.of(context)!.openUserPage(user.id!);
+            MainController.of(context)!.openUserPage(user.id);
             onTap();
           },
         );
@@ -185,6 +185,5 @@ class _SearchResultsWidget extends StatelessWidget {
           },
         );
     }
-    throw Exception("Unreachable statement!");
   }
 }

lib/ui/widgets/tablet_mode/memberships_panel.dart

@@ -105,8 +105,6 @@ class _MembershipsPanelState extends SafeState<MembershipsPanel> {
       case MembershipType.CONVERSATION:
         return _buildConversationMembership(membership);
     }
-
-    throw Exception("Unreachable statement!");
   }
 
   // TODO : add private messages icon support
@@ -156,7 +154,7 @@ class _MembershipsPanelState extends SafeState<MembershipsPanel> {
         leading: AccountImageWidget(user: user, width: _MembershipIconsWidth),
         title: Text(user.displayName),
         subtitle: subtitle,
-        onTap: () => MainController.of(context)!.openUserPage(user.id!),
+        onTap: () => MainController.of(context)!.openUserPage(user.id),
       ),
     );
   }
@@ -237,7 +235,7 @@ class _MembershipsPanelState extends SafeState<MembershipsPanel> {
             SizedBox(width: 5),
             Expanded(
               child: Text(ConversationsHelper.getConversationName(
-                  conversation, _usersList)!),
+                  conversation, _usersList)),
             ),
           ],
         ),

lib/ui/widgets/tour/tour_notifications_pane.dart

@@ -27,7 +27,7 @@ class TourNotificationsPane extends PresentationPane {
             onConfigured: onConfigured,
             onChanged: onChanged,
           ),
-          canGoNext: pushNotificationsKey?.currentState?.canSubmit ?? false,
+          canGoNext: pushNotificationsKey.currentState?.canSubmit ?? false,
           onTapNext: (c) => pushNotificationsKey.currentState!.submit(),
           visible: visible,
         );