fix(device_info_plus): device memory null error on Safari and Firefox (…

…#3401)

Co-authored-by: Miguel Beltran <m@beltran.work>

packages/device_info_plus/device_info_plus/lib/src/device_info_plus_web.dart

@@ -29,7 +29,7 @@ class DeviceInfoPlusWebPlugin extends DeviceInfoPlatform {
           'appCodeName': _navigator.appCodeName,
           'appName': _navigator.appName,
           'appVersion': _navigator.appVersion,
-          'deviceMemory': _navigator.deviceMemory,
+          'deviceMemory': _navigator.safeDeviceMemory,
           'language': _navigator.language,
           'languages': _navigator.languages.toDart,
           'platform': _navigator.platform,
@@ -45,3 +45,16 @@ class DeviceInfoPlusWebPlugin extends DeviceInfoPlatform {
     );
   }
 }
+
+/// Some Navigator properties are not fully supported in all browsers.
+/// However, package:web does not provide a safe way to access these properties,
+/// and assumes they are always not null.
+///
+/// This extension provides a safe way to access these properties.
+///
+/// See: https://github.com/dart-lang/web/issues/326
+///      https://github.com/fluttercommunity/plus_plugins/issues/3391
+extension SafeNavigationGetterExtensions on html.Navigator {
+  @JS('deviceMemory')
+  external double? get safeDeviceMemory;
+}