am 2f8d7a9f: Merge change 21036 into donut

Merge commit '2f8d7a9fffe7e6c01900a4c59a8567e8ca00264f' into eclair

* commit '2f8d7a9fffe7e6c01900a4c59a8567e8ca00264f':
  Also display error on empty minSdkVersion for preview targets.