Fix mustella DateSpinner test RTEs.  Handle the case where the font isn't embedded correctly and the label length is 0.  The DataSpinner will be missing text but it should not RTE.  Currently this is the case for the zh_CN tests since we don't have an open source font.

git-svn-id: https://svn.apache.org/repos/asf/flex/sdk/branches/develop@1434491 13f79535-47bb-0310-9956-ffa450edef68