[ffigen] allow isA (null) to return false for ObjCobject

[Cairo09]

Fixes Issue: #2877

Details

1. Made isA nullable with ObjCObject? and returning false if null input in objc_interface.dart
2. regenerated the related auto-generated files
3. Made isA nullable in existing /test and /example files where isA was called (ffigen and swiftgen)
4. Added check for nullability for isA in is_instance_test.dart

[liamappelbe]

Looks good. This just needs some changelog entries and version bumps:

• FFIgen just needs a CHANGELOG.md entry
• objective_c needs a minor version bump, to 9.4.0-wip, in the pubspec.yaml, and a corresponding CHANGELOG.md entry
• No changelog entry needed for swiftgen

[Cairo09]

Ok. I’ll version bump objective_c and add the FFIgen objective_c changelog entry in the next commit.

[github-actions]

PR Health

License Headers ✔️

// Copyright (c) 2026, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

Files
no missing headers

All source files should start with a license header.

Unrelated files missing license headers

Files
pkgs/hooks_runner/test_data/download_assets/hook/build.dart
pkgs/jni/test/debug_release_test.dart
pkgs/objective_c/example/command_line/lib/main.dart
pkgs/objective_c/lib/src/ns_input_stream.dart

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API leaks ✔️

The following packages contain symbols visible in the public API, but not exported by the library. Export these symbols or remove them from your publicly visible API.

Package	Leaked API symbol	Leaking sources

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Breaking changes ✔️

Package	Change	Current Version	New Version	Needed Version	Looking good?
objective_c	None	9.3.0	9.4.0-wip	9.4.0-wip	✔️

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Changelog Entry ✔️

Package	Changed Files

Changes to files need to be accounted for in their respective changelogs.

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[liamappelbe]

Looks like you need to dart format your code. Remember to always dart format and dart analyze your code before pushing it. Saves time.

It's a bit weird though. FFIgen is supposed to auto-format the bindings when they're regenerated. I'm guessing they were manually updated instead of regenerated?