handle empty chunks in electric.load_series()
handle empty chunks in electric.load_series()

pauldeng/nilmtk,nilmtk/nilmtk,nilmtk/nilmtk,jaduimstra/nilmtk,AlexRobson/nilmtk,josemao/nilmtk,HarllanAndrye/nilmtk,mmottahedi/nilmtk