How to interprate type3 test with 0 df?

#1
I got a problem to interpret these output.

LR Statistics For Type 3 Analysis

Chi-
Source DF Square Pr > ChiSq

period 1 0.11 0.7427
happy 1 0.01 0.9399
agec 2 0.04 0.9812
agrp 2 0.02 0.9906
agec*agrp 0 0.00 .

In my project, I want to use poisson regression model to fit my data. When I do the type3 test to see the significant of the variables, I got this output. Why the variable agec*agrp has 0 df and no p-value? How to interpret this?
Thanks.