Bitbucket new branch from master give wrong ref on context

Hi,

I try to create new branch from master, say it is feature/testagain. This is the response body from Bitbucket webhook:

{
  "id": 949,
  "repo_id": 1606,
  "trigger": "@hook",
  "number": 110,
  "status": "pending",
  "event": "push",
  "action": "",
  "link": "https://bitbucket.org/a-slug/repo-name/commits/a3daa180f74500dbd665c745348f4b9943a6e25f",
  "timestamp": 0,
  "message": "another try\n",
  "before": "",
  "after": "a3daa180f74500dbd665c745348f4b9943a6e25f",
  "ref": "refs/heads/feature/testagain",
  "source_repo": "",
  "source": "feature/testagain",
  "target": "feature/testagain",
  "author_login": "",
  "author_name": "A Name",
  "author_email": "email@domain.com",
  "author_avatar": "https://secure.gravatar.com/avatar/42fde7df94d52d48ae999f0eba239c45?d=https%3A%2F%2Favatar-management--avatars.us-west-2.prod.public.atl-paas.net%2Finitials%2FBP-5.png",
  "sender": "",
  "started": 0,
  "finished": 0,
  "created": 1574548289,
  "updated": 1574548289,
  "version": 1
}

But this is the context variable echoed from a step:

+ echo ""context"(build = "build"(action = "", after = "a3daa180f74500dbd665c745348f4b9943a6e25f", author_avatar = "https://secure.gravatar.com/avatar/42fde7df94d52d48ae999f0eba239c45?d=https%3A%2F%2Favatar-management--avatars.us-west-2.prod.public.atl-paas.net%2Finitials%2FBP-5.png", author_email = "email@domain.com", author_login = "", author_name = "A Name", before = "48dcb0876e4a704cb75e8ae5a6a53c5edfc8f42d", branch = "master", commit = "a3daa180f74500dbd665c745348f4b9943a6e25f", cron = "", environent = "", event = "push", link = "https://bitbucket.org/a-slug/repo-name/commits/a3daa180f74500dbd665c745348f4b9943a6e25f", message = "another try\n", params = {}, ref = "refs/heads/master", sender = "", source = "master", source_repo = "", target = "master", title = ""), repo = "repo"(active = True, branch = "master", config = ".drone.star", git_http_url = "https://bitbucket.org/a-slug/repo-name.git", git_ssh_url = "git@bitbucket.org:a-slug/repo-name.git", ignore_forks = False, ignore_pull_requests = False, link = "https://bitbucket.org/a-slug/repo-name", name = "repo-name", namespace = "a-slug", private = True, protected = False, slug = "a-slug/repo-name", trusted = False, uid = "{24139f0f-ff22-4b0c-bda3-3e7b3f48098a}", visibility = "private"))"
context(build = build(action = , after = a3daa180f74500dbd665c745348f4b9943a6e25f, author_avatar = https://secure.gravatar.com/avatar/42fde7df94d52d48ae999f0eba239c45?d=https%3A%2F%2Favatar-management--avatars.us-west-2.prod.public.atl-paas.net%2Finitials%2FBP-5.png, author_email = email@domain.com, author_login = , author_name = A Name, before = 48dcb0876e4a704cb75e8ae5a6a53c5edfc8f42d, branch = master, commit = a3daa180f74500dbd665c745348f4b9943a6e25f, cron = , environent = , event = push, link = https://bitbucket.org/a-slug/repo-name/commits/a3daa180f74500dbd665c745348f4b9943a6e25f, message = another try
/usr/drone/bin/init: line 26: , params = {}, ref = refs/heads/master, sender = , source = master, source_repo = , target = master, title = ), repo = repo(active = True, branch = master, config = .drone.star, git_http_url = https://bitbucket.org/a-slug/repo-name.git, git_ssh_url = git@bitbucket.org:a-slug/repo-name.git, ignore_forks = False, ignore_pull_requests = False, link = https://bitbucket.org/a-slug/repo-name, name = repo-name, namespace = a-slug, private = True, protected = False, slug = a-slug/repo-name, trusted = False, uid = {24139f0f-ff22-4b0c-bda3-3e7b3f48098a}, visibility = private)): not found

Why ref parameter from context is refs/heads/master?
This behaviour create a failed build each time I want to create new branch from master.

This is my .drone.star:

def main(ctx):
    print(ctx)
    secrets_val = [
        {"name": "A_SECRET", "path": "secret/data/foo", "key": "bar"},
    ]
    steps=[]
    steps.extend([
        init(ctx),
    ])
    drone=[]
    drone.extend(secrets(secrets_val))
    drone.extend([pipeline(ctx, steps)])
    return drone

def pipeline(ctx, steps):
    pipeline={
        "kind": "pipeline",
        "name": "%s" % ctx.repo.name,
        "trigger": {
            "ref": [
                "refs/heads/master",
                "refs/heads/develop",
                "refs/heads/feature/*",
                "refs/heads/hotfix/*"
            ],
            "event": {
                "include": [
                    "push",
                ],
                "exclude": [
                    "tag",
                ]
            },
        },
        "steps": [],
    }
    pipeline["steps"].extend(steps)
    return pipeline

def secrets(values):
    val = []
    for content in values:
        val.append(
            {
                "kind": "secret",
                "name": content["name"],
                "get": 
                    {
                        "path": content["path"],
                        "name": content["key"],
                    }
            }
        )
    return val

def init(ctx):
    return {
        "name": "initialize",
        "image": "alpine",
        "commands": [
            "echo \"%s\"" % ctx,
        ]
    }