Fixed crashing null check bug in camera_web because of accessing a non-nullable field on browsers without facingMode available

Author: jalen-videotape

packages/camera/camera_web/lib/src/camera_service.dart

@@ -200,11 +200,11 @@ class CameraService {
 
       // A list of facing mode capabilities as
       // the camera may support multiple facing modes.
-      final List<String> facingModeCapabilities = videoTrackCapabilities
-          .facingMode
-          .toDart
-          .map((JSString e) => e.toDart)
-          .toList();
+      final List<String> facingModeCapabilities =
+          videoTrackCapabilities.facingModeNullable?.toDart
+              .map((JSString e) => e.toDart)
+              .toList() ??
+          <String>[];
 
       if (facingModeCapabilities.isNotEmpty) {
         final String facingModeCapability = facingModeCapabilities.first;

packages/camera/camera_web/lib/src/pkg_web_tweaks.dart

@@ -31,6 +31,9 @@ extension NonStandardFieldsOnMediaTrackCapabilities on MediaTrackCapabilities {
 
   @JS('torch')
   external JSArray<JSBoolean>? get torchNullable;
+
+  @JS('facingMode')
+  external JSArray<JSString>? get facingModeNullable;
 }
 
 /// Adds missing fields to [MediaTrackSettings]