Adapt banner to large screens

lib/ui/widgets/banner_widget.dart

@@ -69,7 +69,7 @@ class _BannerWidgetState extends State<BannerWidget> {
                         : Icons.warning,
               ),
             ),
-            Flexible(
+            Expanded(
               child: Text(
                 banner.message.containsKey(shortLang)
                     ? banner.message[shortLang]
@@ -105,6 +105,7 @@ class BannerButton extends StatelessWidget {
     return IconButton(
       onPressed: onPressed,
       icon: icon,
+      color: Colors.white,
       disabledColor: Colors.white,
       padding: EdgeInsets.all(1.0),
     );