Improper handling of empty .json files

[Paul Tiplady]

paul@ubuntu:~/gulfstream/systemtest$ touch /tmp/pyrasite-59506-objects.json
paul@ubuntu:~/gulfstream/systemtest$ ../env/bin/pyrasite-memory-viewer 59506
Traceback (most recent call last):
  File "../env/bin/pyrasite-memory-viewer", line 9, in <module>
    load_entry_point('pyrasite==2.0', 'console_scripts', 'pyrasite-memory-viewer')()
  File "/home/paul/gulfstream/env/local/lib/python2.7/site-packages/pyrasite/tools/memory_viewer.py", line 150, in main
    objects = loader.load(filename)
  File "/home/paul/gulfstream/env/local/lib/python2.7/site-packages/meliae/loader.py", line 542, in load
    max_parents=max_parents)
  File "/home/paul/gulfstream/env/local/lib/python2.7/site-packages/meliae/loader.py", line 621, in _load
    factory=objs.add):
  File "/home/paul/gulfstream/env/local/lib/python2.7/site-packages/meliae/loader.py", line 615, in iter_objs
    % (line_num, len(objs), mb_read, input_mb, tdelta))
UnboundLocalError: local variable 'line_num' referenced before assignment

This error case should probably be handled in an assert, rather than silently assuming that the file has lines and then blowing up later .