Please run below to check each line of your label files. Make sure there is not empty line too.
import glob
rootdir = "./label"
for i in glob.glob(rootdir + "/*.txt"):
with open(i, 'r') as j:
for line in j.readlines():
label = line.strip()
length = len(label.split(" "))
print("This label have {} fields".format(length))
assert length == 15, 'Ground truth kitti labels should have only 15 fields. And make sure there is not empty lines. Please check the label in the file %s' % (j)