_atspi_dbus_handle_event(): return early if the category or interface name is NULL
_atspi_dbus_handle_event(): return early if the category or interface name is NULL

I don't know why the interface would be NULL, but
dbus_message_get_interface() can return that.

We return DBUS_HANDLER_RESULT_NOT_YET_HANDLED in the same way as the
other error case, but note that the caller of this function ignores
the return value.

GNOME/at-spi2-core,GNOME/at-spi2-core,GNOME/at-spi2-core