Objects (such as networks) won't have an empty or null EA value.  Instead the EA will not be defined for the network.

Consider if there is a large number of EAs defined in the grid, we don't want to automatically store an empty value for all possible EAs.

However there doesn't seem to be a way to filter for networks where a specific EA is not defined.

Instead you would need to get the full list and parse on your own for networks that don't have the VLAN EA defined.