Improved server version check

lib/classes/process_modal.dart

@@ -1,20 +1,14 @@
+import 'package:adguard_home_manager/config/globals.dart';
 import 'package:flutter/material.dart';
 
 import 'package:adguard_home_manager/widgets/process_dialog.dart';
 
 class ProcessModal {
-  late BuildContext context;
-
-  ProcessModal({
-    required this.context
-  });
-
   void open(String message) async {
     await Future.delayed(const Duration(seconds: 0), () => {
       showDialog(
-        context: context, 
-        builder: (c) {
-          context = c;
+        context: globalNavigatorKey.currentContext!, 
+        builder: (ctx) {
           return ProcessDialog(
             message: message,
           );
@@ -26,6 +20,6 @@ class ProcessModal {
   }
 
   void close() {
-    Navigator.pop(context);
+    Navigator.pop(globalNavigatorKey.currentContext!);
   }
 }