Fix possible null pointer dereference and unintended integer division #1641

	# This is a copy of ci-unix-shared-local.yml for building shared libraries
	# with an additional build configuration (using installed deps and dav1d).

	name: CI MinGW
	on: [push, pull_request]

	permissions:
	contents: read

	# Cancel the workflow if a new one is triggered from the same PR, branch, or tag, except on main.
	concurrency:
	group: ${{ github.workflow }}-${{ github.ref }}
	cancel-in-progress: ${{ github.ref != 'refs/heads/main' }}

	jobs:
	build-mingw:
	runs-on: windows-latest
	strategy:
	fail-fast: false
	matrix:
	sys:
	- mingw64
	- ucrt64
	- clang64

	defaults:
	run:
	shell: msys2 {0}
	steps:
	- uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
	- uses: msys2/setup-msys2@v2
	with:
	msystem: ${{ matrix.sys }}
	update: true
	install: >-
	git
	pacboy: >-
	aom:p
	cmake:p
	diffutils:p
	cc:p
	dav1d:p
	imagemagick:p
	libjpeg-turbo:p
	libpng:p
	libyuv:p
	ninja:p
	zlib:p
	- uses: ./.github/actions/cache
	with:
	extra-key: ${{ matrix.sys }}
	- name: Print cmake version
	run: cmake --version

	- name: Prepare libavif (cmake)
	run: >
	cmake -G Ninja -S . -B build
	-DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=OFF
	-DAVIF_CODEC_AOM=SYSTEM
	-DAVIF_CODEC_AOM_DECODE=OFF -DAVIF_CODEC_AOM_ENCODE=ON
	-DAVIF_CODEC_DAV1D=SYSTEM
	-DAVIF_LIBSHARPYUV=LOCAL -DAVIF_LIBYUV=SYSTEM
	-DAVIF_BUILD_EXAMPLES=ON -DAVIF_BUILD_APPS=ON
	-DAVIF_BUILD_TESTS=ON -DAVIF_ENABLE_GTEST=ON -DAVIF_GTEST=LOCAL
	-DAVIF_BUILD_GDK_PIXBUF=ON
	-DAVIF_ENABLE_WERROR=ON
	- name: Build libavif (ninja)
	working-directory: ./build
	run: ninja
	- name: Run AVIF Tests
	working-directory: ./build
	run: ctest -j --output-on-failure

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