Locked maps create excess map IDs

When locking multiple maps of the same map ID, the game creates an unnecessary excess of new map IDs.

Steps to reproduce:

1. Create a filled map, then make duplicate(s), so you have at least two maps of the same ID (for example, two ID #3 maps)

2. Lock each map separately in a cartography table, one after the other.

3. Instead of multiple ID #4 maps, the game creates ID #4, ID #5, etc...

This seems wasteful and inefficient, consuming the finite number of available map IDs on otherwise identical maps.