GraphQL mutation fails with "fileDeletions[]" parameter error

## Bug Report: GraphQL mutation fails with "fileDeletions[]" parameter error

### Description
The `grafana/github-api-commit-action@v1.0.0` action is failing when attempting to create a commit via GraphQL mutation. The error indicates that the `fileDeletions[]` field requires a value separated by an '=' sign.

### Expected Behavior
The action should successfully commit the staged files (`chart/README.md` and `chart/values.schema.json`) to the repository without errors.

### Actual Behavior
The action fails with the following error:
```
field "fileDeletions[]" requires a value separated by an '=' sign
Error: Process completed with exit code 1.
```

### Steps to Reproduce
1. Use the `grafana/github-api-commit-action@v1.0.0` action with the following configuration:
```yaml
- name: Commit changes
uses: grafana/github-api-commit-action@v1.0.0
with:
token: ${{ secrets.GITHUB_TOKEN }}
commit-message: "docs: helm-docs automated action [skip ci]"
stage-all-files: true
create-branch-on-remote: false
success-if-no-changes: false
```

2. Have modified files in the repository (in this case, `chart/README.md` and a new file `chart/values.schema.json`)
3. Run the workflow

### Environment
- **Action Version**: v1.0.0
- **Runner**: GitHub Actions (ubuntu-latest)
- **Files being committed**:
- Modified: `chart/README.md`
- Added: `chart/values.schema.json`

### Error Logs
```
Run grafana/github-api-commit-action@v1.0.0
with:
token: ***
commit-message: docs: helm-docs automated action [skip ci]
stage-all-files: true
create-branch-on-remote: false
success-if-no-changes: false

Run # Get the remote URL (default "origin")
Remote URL: https://github.com//

Run git add .
git add .

Run status_output=$(git status --porcelain=v2 --branch --untracked-files=no)
status: M.
filepath: chart/README.md
status: A.
filepath: chart/values.schema.json

Run branch_oid=$(git ls-remote https://x-access-token:${GH_TOKEN}@github.com/${REPO}.git refs/heads/${BRANCH} | awk '{ print $1 }')

mutation( $repo: String!, $branch: String!, $commitMessage: String!, $expectedHeadOid: GitObjectID!, $fileAdditions: [FileAddition!]!, $fileDeletions: [FileDeletion!]!) { createCommitOnBranch( input: { branch: { repositoryNameWithOwner: $repo, branchName: $branch }, message: { headline: $commitMessage }, fileChanges: { additions: $fileAdditions, deletions: $fileDeletions }, expectedHeadOid: $expectedHeadOid } ){ commit { url, changedFilesIfAvailable } } }

field "fileDeletions[]" requires a value separated by an '=' sign
Error: Process completed with exit code 1.
```

### Analysis
The issue appears to be in the GraphQL mutation handling. The action is trying to pass a `fileDeletions` parameter to the `createCommitOnBranch` mutation, but the parameter seems to be malformed or empty, causing the GraphQL API to reject it.