Make JS object skip null value.
Make JS object skip null value.

Signed-off-by: Toha <cf051a78db80d0ace1965fe83f485d0a116df2c8@yahoo.com>

Perturbatio/mysql-workbench-schema-exporter,johmue/mysql-workbench-schema-exporter,gigablah/mysql-workbench-schema-exporter,molaux/mysql-workbench-schema-exporter,awallef/mysql-workbench-schema-exporter,zando-coza/mysql-workbench-schema-exporter,WitteStier/mysql-workbench-schema-exporter,johmue/mysql-workbench-schema-exporter,WitteStier/mysql-workbench-schema-exporter,cesaric/mysql-workbench-schema-exporter,cesaric/mysql-workbench-schema-exporter,molaux/mysql-workbench-schema-exporter,mysql-workbench-schema-exporter/mysql-workbench-schema-exporter,vukanac/mysql-workbench-schema-exporter,vukanac/mysql-workbench-schema-exporter,zando-coza/mysql-workbench-schema-exporter,gigablah/mysql-workbench-schema-exporter,awallef/mysql-workbench-schema-exporter,Lakhman/mysql-workbench-schema-exporter,Perturbatio/mysql-workbench-schema-exporter,defyasdf/mysql-workbench-schema-exporter,turnaev/mysql-workbench-schema-exporter,defyasdf/mysql-workbench-schema-exporter,mysql-workbench-schema-exporter/mysql-workbench-schema-exporter