All ERT stations have space tiles beneath walls

### Testmerges

doesnt matter

### Round ID

irrelevant

### Description of the bug

All ERT stations have space tiles beneath walls

### What's the difference with what should have happened?

There should be floor tiles.

### How do we reproduce this bug?

1. spawn ert station
2. dismantle a wall
3. float in space
...

### Issue Bingo

- [X] Issue could be reproduced at least once
- [X] Issue happened in a recent (less than 7 days ago) round
- [X] Couldn't find an existing issue about this (https://github.com/cmss13-devs/cmss13/issues)