null safety

lib/pages/widgets/local_button.dart

@@ -6,13 +6,13 @@ import 'package:flutter/material.dart';
 import 'callbacks.dart';
 
 class LocalButton extends StatelessWidget {
-  final CallBack callBack;
-  final IconData iconData;
-  final String textKey;
-  final Color color;
+  final CallBack? callBack;
+  final IconData? iconData;
+  final String? textKey;
+  final Color? color;
 
   const LocalButton(
-      {Key key,
+      {Key? key,
       this.callBack,
       this.iconData,
       this.textKey,
@@ -33,7 +33,7 @@ class LocalButton extends StatelessWidget {
           minWidth: 900.0,
           height: 100.0,
           child: FlatButton(
-            onPressed: callBack == null ? null : () => callBack(),
+            onPressed: callBack == null ? null : () => callBack!(),
             child: Row(
               mainAxisAlignment: MainAxisAlignment.center,
               children: [
@@ -48,7 +48,7 @@ class LocalButton extends StatelessWidget {
                 ),
                 LocalText(
                   context,
-                  textKey,
+                  textKey!,
                   color: Colors.white,
                   fontSize: 16,
                 ),