tester: reject empty argument for -l #2609

	---
	name: Ubuntu

	on:
	pull_request:
	push:
	branches:
	- master

	jobs:
	tests:
	env:
	COLORTERM: truecolor
	NPROC: 2
	TERM: xterm
	name: 🐧 build, test, & install
	runs-on: ubuntu-latest

	steps:

	- name: Install tools and libraries via APT
	run: \|
	sudo apt update
	sudo apt install -y \
	build-essential \
	cmake \
	doctest-dev \
	ffmpeg \
	libavdevice-dev \
	libdeflate-dev \
	libncurses-dev \
	libqrcodegen-dev \
	libswscale-dev \
	libunistring-dev \
	pandoc \
	pkg-config \
	python3-cffi \
	python3-dev \
	python3-setuptools

	- uses: actions/checkout@v2

	- name: cmake
	run: \|
	mkdir build && cd build
	cmake .. \
	-DCMAKE_BUILD_TYPE=Release \
	-DUSE_QRCODEGEN=on

	- name: make
	run: \|
	cd build
	make -j${NPROC}

	- name: ctest
	run: \|
	cd build
	ctest --output-on-failure

	- name: make install
	run: \|
	cd build
	sudo make install
	sudo ldconfig

	- name: python wrappers (old)
	run: \|
	python3 -m pip install --upgrade pip
	pip install pypandoc
	cd cffi
	python3 setup.py sdist build
	sudo python3 setup.py install
	notcurses-pydemo > /dev/null
	ncdirect-pydemo > /dev/null

	- name: python wrappers (new)
	run: \|
	cd python
	python3 setup.py build
	sudo python3 setup.py install
	python3 examples/000-print-version.py

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