Generate Ensemble Statistics can fail if the initial data is NOT read from a .dream3d file

If a pipeline starts by reading an EBSD file and proceeds through the reconstruction and statistics phases and then a user attempts to use the "Generate Ensemble Statistics" filter they will be unable to select the phase types because that information is not available. If the initial data is read from a .dream3d file then the number of phases is known because we are reading a know array from the file.