fix getCapabilities for Firefox

@@ -18,7 +18,14 @@ final class MediaTrackConstraintsDelegate {
 
     final MediaStreamTrack track = tracks.first;
 
-    final MediaTrackCapabilities capabilities = track.getCapabilities();
+    final MediaTrackCapabilities capabilities;
+
+    if (track.getCapabilitiesNullable != null) {
+      capabilities = track.getCapabilities();
+    } else {
+      capabilities = MediaTrackCapabilities();
+    }
+
     final MediaTrackSettings settings = track.getSettings();
     final JSArray<JSString>? facingModes = capabilities.facingModeNullable;
 

 import 'dart:js_interop';
 import 'package:web/web.dart';
 
+/// This extension provides nullable properties for [MediaStreamTrack],
+/// for cases where the properties are not supported by all browsers.
+extension NullableMediaStreamTrackCapabilities on MediaStreamTrack {
+  /// The `getCapabilities` function is not supported on Firefox.
+  @JS('getCapabilities')
+  external JSFunction? get getCapabilitiesNullable;
+}
+
 /// This extension provides nullable properties for [MediaTrackCapabilities],
 /// for cases where the properties are not supported by all browsers.
 extension NullableMediaTrackCapabilities on MediaTrackCapabilities {

@@ -125,7 +125,14 @@ class MobileScannerWeb extends MobileScannerPlatform {
     }
 
     final MediaStreamTrack videoTrack = tracks.first;
-    final MediaTrackCapabilities capabilities = videoTrack.getCapabilities();
+    final MediaTrackCapabilities capabilities;
+
+    if (videoTrack.getCapabilitiesNullable != null) {
+      capabilities = videoTrack.getCapabilities();
+    } else {
+      capabilities = MediaTrackCapabilities();
+    }
+
     final JSArray<JSString>? facingModes = capabilities.facingModeNullable;
 
     // TODO: this is an empty array on MacOS Chrome, where there is no facing mode, but one, user facing camera.