fix: check empty registry name #1641

	# Copyright The ORAS Authors.
	# Licensed under the Apache License, Version 2.0 (the "License");
	# you may not use this file except in compliance with the License.
	# You may obtain a copy of the License at
	#
	# http://www.apache.org/licenses/LICENSE-2.0
	#
	# Unless required by applicable law or agreed to in writing, software
	# distributed under the License is distributed on an "AS IS" BASIS,
	# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	# See the License for the specific language governing permissions and
	# limitations under the License.

	name: build

	on:
	push:
	branches:
	- main
	- release-*
	pull_request:
	branches:
	- main
	- release-*

	jobs:
	build:
	runs-on: ubuntu-latest
	strategy:
	matrix:
	go-version: ['1.21', '1.22']
	fail-fast: true
	steps:
	- name: Checkout
	uses: actions/checkout@v4
	- name: Set up Go ${{ matrix.go-version }} environment
	uses: actions/setup-go@v5
	with:
	go-version: ${{ matrix.go-version }}
	check-latest: true
	- name: Run unit tests
	run: make test
	- name: Upload coverage to codecov.io
	uses: codecov/codecov-action@v3

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