Getting Squares in my query results

[R2D2]

I'm trying to create a query which pulls the value of a combo box on my main form into a column. This combo box has the default value of 12. For some reason, the query works fine if the user selects a value in the combo box (even if they simply re-select the default value). But if the user doesn't select a value, the query returns squares (like this: ) rather than the value in the combo box (which is the default value of 12, since the user hasn't changed it).

How do I fix this?

Thanks!