Clean up code warnings

lib/ui/app/buttons/elevated_button.dart

@@ -18,10 +18,15 @@ class AppButton extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final button = RaisedButton(
-      padding: EdgeInsets.symmetric(vertical: 14, horizontal: 14),
-      color: color ?? Theme.of(context).buttonColor,
-      shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(5)),
+    final button = ElevatedButton(
+      style: ElevatedButton.styleFrom(
+          primary: color ?? Theme.of(context).buttonColor,
+          padding: EdgeInsets.symmetric(vertical: 14, horizontal: 14),
+          shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(5)),
+          elevation: 4,
+          textStyle: TextStyle(
+            color: Colors.white,
+          )),
       child: iconData != null
           ? IconText(
               icon: iconData,
@@ -29,8 +34,6 @@ class AppButton extends StatelessWidget {
               alignment: MainAxisAlignment.center,
             )
           : Text(label, overflow: TextOverflow.ellipsis),
-      textColor: Colors.white,
-      elevation: 4.0,
       onPressed: () => onPressed(),
     );
 

lib/ui/app/main_screen.dart

@@ -9,7 +9,6 @@ import 'package:invoiceninja_flutter/redux/dashboard/dashboard_actions.dart';
 import 'package:invoiceninja_flutter/redux/reports/reports_actions.dart';
 import 'package:invoiceninja_flutter/redux/settings/settings_actions.dart';
 import 'package:invoiceninja_flutter/redux/ui/pref_state.dart';
-import 'package:invoiceninja_flutter/ui/app/app_shortcuts.dart';
 import 'package:invoiceninja_flutter/ui/app/blank_screen.dart';
 import 'package:invoiceninja_flutter/ui/app/change_layout_banner.dart';
 import 'package:invoiceninja_flutter/ui/app/confirm_email_vm.dart';

lib/ui/app/system_log_viewer.dart

@@ -45,7 +45,9 @@ class _SystemLogViewerState extends State<SystemLogViewer> {
             if (systemLog.log.isNotEmpty) {
               try {
                 logs = json.decode(systemLog.log);
-              } catch (e) {}
+              } catch (e) {
+                // do nothing
+              }
             }
 
             return ExpansionPanel(