#60: Removed null value when no url present
#60: Removed null value when no url present

* Component table previously showed the text null when no url was
  provided in the component modal. This fix shows an empty cell
  when no url is provided by the user.

Signed-off-by: Jillian Daguil <8e927abf8e72a52d2816b020862fa1a32fbeb0d6@nexb.com>

nexB/aboutcode-manager,nexB/aboutcode-manager,nexB/aboutcode-manager