*** Error in `python': free(): invalid pointer: 0x0000000001ad2420 ***

Question

I am running with a simple python script which is giving

*** Error in `python': free(): invalid pointer: 0x00000000029b7420 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x777e5)[0x7f23d6dc67e5]
/lib/x86_64-linux-gnu/libc.so.6(+0x8037a)[0x7f23d6dcf37a]
/lib/x86_64-linux-gnu/libc.so.6(cfree+0x4c)[0x7f23d6dd353c]
/usr/lib/x86_64-linux-gnu/libprotobuf.so.9(_ZN6google8protobuf8internal28DestroyDefaultRepeatedFieldsEv+0x1f)[0x7f23ae6e18af]
/usr/lib/x86_64-linux-gnu/libprotobuf.so.9(_ZN6google8protobuf23ShutdownProtobufLibraryEv+0x8b)[0x7f23ae6e0b3b]
/usr/lib/x86_64-linux-gnu/libmirprotobuf.so.3(+0x233b9)[0x7f2398fc03b9]
/lib64/ld-linux-x86-64.so.2(+0x10de7)[0x7f23d7346de7]
/lib/x86_64-linux-gnu/libc.so.6(+0x39ff8)[0x7f23d6d88ff8]
/lib/x86_64-linux-gnu/libc.so.6(+0x3a045)[0x7f23d6d89045]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf7)[0x7f23d6d6f837]
python(_start+0x29)[0x4933e9]

My sample code is

import sys
sys.path.append('../../python')
import caffe
import io
from PIL import Image
import numpy as np
import math
import leveldb

video_list = 'images/test_list.txt'
f = open(video_list, 'r')
f_lines = f.readlines()
f.close()

linenum = 0
predict_right = 0;
db1 = leveldb.LevelDB('./rgb_test_rst')
db2 = leveldb.LevelDB('./depth_test_rst')
datum1 = caffe.proto.caffe_pb2.Datum()
datum2 = caffe.proto.caffe_pb2.Datum()
for idx, line in enumerate(f_lines):
  key_str = '%06d' %(linenum)
  value1 = db1.Get(key_str)
  value2 = db2.Get(key_str)
  datum1.ParseFromString(value1)
  datum2.ParseFromString(value2)

. . . Running with Ubuntu 16.04, Numpy 1.14.0. Python 2.7

Further, i have checked my all files are reads correctly from text file.