Fresh install of Magento 2.1.3 with Lumo sample data has no records to edit in Content > Design > Configuration.
A better way to fix this is to run the reindexer command:
bin/magento indexer:reindex design_config_grid
This will update the
design_config_grid_flat with the correct values for your site. If you get a message that the index is locked you may need to reset it with:
bin/magento indexer:reset design_config_grid
May be , your magento instance does not installed properly that why it is created issue.
IN magento 2.1.3 ,
Content > Design >Config section does not exit.
You can see at ,
You can see theme assignment at Content > Theme >Config
Please check design_config_grid_flat table data.
If does have then run this query
INSERT INTO `design_config_grid_flat` VALUES ('0',NULL,NULL,NULL,''),('1','1',NULL,NULL,''),('2','1','1','1','');