title: Bitbucket Pipeline fails saying that step is empty, null or missing
body: <p>I'm trying to configure a Bitbucket pipeline to execute the SonarQube pipe, but Bitbucket complains that the pipeline step is empty, null or missing.</p>
  
  <p>I've got SONAR_TOKEN defined as a project variable with the correct token.</p>
  
  <p>Here's my current bitbucket-pipeline.yml file:</p>
  
  <pre><code>image: atlassian/default-image:2
  
  clone:
    depth: full
  
  definitions:
    caches:
      sonar: ~/.sonar/cache
    steps:
      - step: &amp;sonarcloud
        name: Analyze on SonarCloud
        caches:
          - sonar
        script:
          - pipe: sonarsource/sonarcloud-scan:0.1.5
            variables:
              SONAR_TOKEN: ${SONAR_TOKEN}
  
  pipelines:
    branches:
      '*':
        - step: *sonarcloud
  </code></pre>
  
  <p>Any ideas?</p>