drivers: usart_zephyr: Check if return_fd is present before assign it #462

	name: FreeRTOS Build and Test
	on: [push, pull_request]
	jobs:
	build-freertos:
	runs-on: ubuntu-latest
	strategy:
	fail-fast: false

	steps:
	- name: Setup build system packages on Linux
	run: \|
	sudo apt-get install ninja-build meson tree

	- name: Checkout Test App
	uses: actions/checkout@v4
	with:
	repository: libcsp/libcsp-freertos

	- name: Checkout FreeRTOS Kernel
	uses: actions/checkout@v4
	with:
	repository: FreeRTOS/FreeRTOS-Kernel
	path: freertos

	- name: Checkout libcsp under subprojects
	uses: actions/checkout@v4
	with:
	path: subprojects/libcsp

	- name: Build it
	run: \|
	meson setup builddir && ninja -C builddir

	- name: Run it
	run: builddir/demo

Provide feedback