Tree overlay hides monster number

[l0ft3r]

Affected Scenario(s): [59 and all scenarios with trees and (flyin creatures or players)]

Describe the bug
The number of the monster is hidden when it is flying over a tree overlay tile.

To Reproduce
Steps to reproduce the behavior:

1. Start scenario 59
2. Move an Imp (or any monster) onto a tree.
3. Note that the number of the monster is no longer visible.

Browser : Chrome

Scenario 59 used as an example

[hobnob]

Should definitely fix this! I'll add it to the next release :-)