No need to open a support ticket.
This is a known issue and caused by -
Corrupted Simple Gateway's multi_realms_for_blades configuration in Database - the multi_realms_for_blades container has an entry with empty realms.
The solution:
1. Close all SmartConsole windows and open GuiDBedit Tool.
2. On the Tables pane select the "Network Objects/network_objects" table.
3. On the right pane select the Simple Gateway object that causes the API failure.
4. On the bottom pane select the multi_realms_for_blades container field.
5. Check if there are entries with empty realms. If yes, right-click on the realm and select "Reset" action from the popup menu.
6. Finally, save the changes.
Robert.