[OPEN] Map editor adding units unknown error

Expected behavior
When I add a new units and set the "Available at turns" option to 0-999 and save, I expect the game to save the unit.

Actual behavior
When you try to save, you get unknown error.

Steps to reproduce the behavior
Create a new unit, set the available at turns to 0-999. Then save the map.

Information:
Browser: N/A

Browser version: N/A
OS: N/A

Any other relevant information:
The unknown error only happens when you set the turn higher than 500.

Attachments:


When I try to save the map.