Lidar LAS files do not raise an exception

[kinverarity1]

Describe the bug
Attempting to open a Lidar LAS file results in lasio (slowly) and incorrectly trying to parse it as a Log ASCII Standard file.

To Reproduce
Steps to reproduce the behavior:

• lasio.read("a_lidar_file.las", ignore_header_errors=True) results in a LASFile object instead of an exception

Expected behavior
An exception should be raised immediately.

Software versions (please complete the following information):

• Python version: 3.7
• Python distribution: Anaconda
• master branch

[kinverarity1]

In fact, doing this in a Jupyter Notebook for a 33 MB lidar file, completely nuked my notebook server 😭