Invalid tag/reference format with ghcr.io

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## Describe the Bug
Hello,
I'm trying to set up a Github Workflow that uses this action to create and publish a docker image to ghcr.io.
I'm getting an error on the `Builder info` step

```
Error: buildx failed with: ERROR: invalid tag "ghcr.io//:sha-8cc8e90c5ebb6ff27df767484b7f95f9d70f3faa": invalid reference format
```

## Expected Behavior
I expect the default tags to work.

## Steps to Reproduce
Whenever a workflow action runs, see below.

## Screenshots
See below

## Environment (please complete the following information):

**My (simplified) workflow config**

```yaml
name: Release
on:
push:
branches:
- main
release:
type: [published]
permissions:
contents: read
packages: write
jobs:
build-and-push-image:
runs-on: ubuntu-latest
steps:
- name: Checkout repository
uses: actions/checkout@v4

- name: Build and push
uses: cloudposse/github-action-docker-build-push@v1.17.2
with:
registry: ghcr.io
login: ${{ github.actor }}
password: ${{ secrets.github_token }}
organization: ${{ github.repository.owner.login }}
repository: ${{ github.repository.name }}

```

## Additional Context

**Error output**

```yaml
/usr/bin/docker buildx build --cache-from type=gha --cache-to type=gha,mode=max --file .//Dockerfile --iidfile /home/runner/work/_temp/docker-actions-toolkit-SPmw6I/build-iidfile-1c3c362c17.txt --label org.opencontainers.image.created=2025-01-14T13:35:44.838Z --label org.opencontainers.image.description=Project description --label org.opencontainers.image.licenses= --label org.opencontainers.image.revision=8baa8e2249f3a8b6e427ef8eecd0847f660d4099 --label org.opencontainers.image.source=https://github.com// --label org.opencontainers.image.title=my-project --label org.opencontainers.image.url=https://github.com/my-org/my-project --label org.opencontainers.image.version=sha-8baa8e2249f3a8b6e427ef8eecd0847f660d4099 --platform linux/amd64 --attest type=provenance,mode=min,inline-only=true,builder-id=https://github.com/my-org/my-project/actions/runs/12768807147 --tag ghcr.io//:sha-8baa8e2249f3a8b6e427ef8eecd0847f660d4099 --tag ghcr.io//:main --tag ghcr.io//:latest --tag ghcr.io//:sha-8baa8e2 --metadata-file /home/runner/work/_temp/docker-actions-toolkit-SPmw6I/build-metadata-e623a3464d.json --pull --push ./
ERROR: invalid tag "ghcr.io//:sha-8baa8e2249f3a8b6e427ef8eecd0847f660d4099": invalid reference format
Error: buildx failed with: ERROR: invalid tag "ghcr.io//:sha-8baa8e2249f3a8b6e427ef8eecd0847f660d4099": invalid reference format
```

Inizia riproducendo il workflow mostrato con cloudposse/github-action-docker-build-push@v1.17.2 e confronta i suoi input con il comando buildx generato. Traccia come i valori del registry, dell’organizzazione e del repository diventano gli image tag; il lavoro è completo quando il workflow produce tag ghcr.io validi senza un percorso vuoto.

Scritto dal modello di indicizzazione a partire dal testo della issue.