[GNC] Another Potential Software Defect

[Robert Simmons]

Lets see if I can go two for two:

Steps to reproduce (using a sqlite file):

1. Run code snippet below.
2. Observe raised exception "<gnc.backend.sql>
[GncSqlColumnTableEntryImpl<Otype>::add_to_query()] Invalid owner type: 0"

import gnucash
import gnucash.gnucash_business

s = gnucash.Session('sqlite3://test.gnucash',
gnucash.SessionOpenMode.SESSION_NORMAL_OPEN)
book = s.book
commod_table = book.get_table()
USD = commod_table.lookup('CURRENCY', 'USD')
cust = gnucash.gnucash_business.Customer(book, '1', USD, 'Darth Vader')
job = gnucash.gnucash_business.Job(book, '1', cust, 'Build Deathstar')