Glass windows can stack

### Testmerges

N/A

### Round ID

N/A

### Description of the bug

Built glass windows. Not the ones that are on window frames.
Can stack creating a dumb makeshift defense with enough of them

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

They shouldn't stack on themselves or other things.

### How do we reproduce this bug?

1. Build a window
2. Build a window
3. Build a window
...

### 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)

Start by reproducing the issue in CM-SS13 by building successive glass windows, then trace the glass-window construction and placement entry points in the game code. Done means a glass window cannot be placed on itself or another object, while the reported reproduction no longer creates stacked defenses.

Written by the indexing model from the issue text.