The generative join chokes on missing data

[Schaechtle]

In a real-world example using the SPPL backend, the following works fine,

    (SELECT * FROM table WHERE age IS NOT NULL)
    GENERATIVE JOIN model GIVEN age

but stops working when the table is not filtered for null conditions.

    (SELECT * FROM table)
    GENERATIVE JOIN model GIVEN age

💡 Reproduced with both SPPL and ClojureCat.