recipetool: create: fix failure handling included dicts

recipetool: create: fix failure handling included dicts

If a setup dict in a python setup.py file pulled in the contents of
another dict (e.g.  **otherdict), then we got an error when mapping
the keys because the key is None in that case. Skip those keys to avoid
the error (we pick up the values directly in any case).

A quick reproducer for this issue:

recipetool create https://files.pythonhosted.org/packages/source/p/pyqtgraph/pyqtgraph-0.10.0.tar.gz

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>