Chances Claim Rooftop Corner OOB

## Testmerges
#11589: 'byondoidc' by hry-gh at commit f188eb6b81
#11660: 'achievement integration' by hry-gh at commit 41b97d8d87
#11677: 'Xenomorph on dropship alert now only occurs after landing' by carlarctg at commit 5d4d3c1257
#11636: 'Fix: Cades stacking on top of each other.' by MistChristmas at commit 03c79f5178
#11615: 'Xeno Fire Immunity Refactor x2 + Hive Fire Resistance Buff' by Drulikar at commit e425813335
#10999: 'Fix of various plane related issues' by Blundir at commit f85a7153c4
#11653: 'Rust_g 6.0.0' by Drulikar at commit 9d5cc62999

## Round ID
32392

## Description of the bug
If you jump up on some rooftop corner tiles in chances claim, you can teleport to different areas, or even stay on the roof.

## What's the difference with what should have happened?
I expected this, after my solaris adventure, but it's here as well. We SHOULD just be sliding back off.

## How do we reproduce this bug?
Find a cornered rooftop, preferably next to walls.

Pounce onto it while looking up.

Profit.

## Attached logs
```
Ancient Runner (SID-620) slams into the ice columns!6
We pounce at the sloped roof!
Ancient Runner (SID-620) slams into the ice columns!4
Ancient Runner (SID-620) slams into the ice columns!11
```

## Additional details
- Author: Acetylene
- Admin: the smellyhippie
- Note: None