[Koha] null itemnumbers and borrowernumbers in issues table

[Jeffrey LePage]

Greetings,

We've just discovered 4 records in the issues table that have nulls where there should never be nulls.  Specifically, 2 records with null borrowernumber and 2 records with null itemnumber.  As a result, there are two overdue books checked out to a NULL patron and two patrons who've checked out NULL books.

I notice that the issues table is constructed thus:
mysql> desc issues;
+-----------------+-------------+------+-----+-------------------+-------+
| Field           | Type        | Null | Key | Default           | Extra |
+-----------------+-------------+------+-----+-------------------+-------+
| borrowernumber  | int(11)     | YES  | MUL | NULL              |       | 
| itemnumber      | int(11)     | YES  | MUL | NULL              |       | 
| date_due        | date        | YES  |     | NULL              |       | 
| branchcode      | varchar(10) | YES  |     | NULL              |       | 
| issuingbranch   | varchar(18) | YES  |     | NULL              |       | 
| returndate      | date        | YES  |     | NULL              |       | 
| lastreneweddate | date        | YES  |     | NULL              |       | 
| return          | varchar(4)  | YES  |     | NULL              |       | 
| renewals        | tinyint(4)  | YES  |     | NULL              |       | 
| timestamp       | timestamp   | NO   |     | CURRENT_TIMESTAMP |       | 
| issuedate       | date        | YES  |     | NULL              |       | 
+-----------------+-------------+------+-----+-------------------+-------+

Notice that borrowernumber and itemnumber are NULL'able.  
Isn't this a _bad_ idea?  I don't know why/how the null itemnumbers and borrowernumbers got into the database, but it seems that making them non-nullable would be a good idea.

Comments?

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