Error when running `mylib` example since d40f96d

[krystophny]

When running the example according to https://f2x.readthedocs.io/en/latest/content/introduction/getting_started.html the following error occurs in master and the previous commit d40f96d:

$~/code/F2x/draft$ F2x -W lib -m mylib.* mylib/test.f90
INFO  F2x Version 0.2
Traceback (most recent call last):
  File "/usr/local/bin/F2x", line 11, in <module>
    load_entry_point('F2x', 'console_scripts', 'F2x')()
  File "/home/calbert/code/F2x/src/F2x/runtime/main.py", line 157, in main
    for template_package in args.register_template:
TypeError: 'NoneType' object is not iterable

With earlier versions this is working fine.