ValueError: invalid literal for int() with base 10: ''

[keames]

It's also worth mentioning that if there is other invalid data in the file, regex may be his only option. It wouldn't be too hard to add to your code, @snippsat.
It's literally just the import and 1 additional line:

import re
validNumPattern = re.compile(r"\A\d+\Z")
with open('numbers.txt') as f:
    for line in f:
        line = line.strip()
        if validNumPattern.search(line):           
            print(int(line))

It can't hurt to be thorough...