Fixed CI issue, card created - empty attrs in FF are null, not empty string.
Fixed CI issue, card created - empty attrs in FF are null, not empty string.

jrwren/juju-gui,mitechie/juju-gui,mitechie/juju-gui,bac/juju-gui,jrwren/juju-gui,mitechie/juju-gui,bac/juju-gui,mitechie/juju-gui,jrwren/juju-gui,jrwren/juju-gui,bac/juju-gui,bac/juju-gui