Brief summary of issue / Description of requested feature:

Mudlet will crash/hang indefinitely if you have a map open and you scroll quickly through the font list under the Mapper preferences tab.

Steps to reproduce the issue / Reasons for adding feature:

1. Open any map with rooms built
2. Open Mudlet preferences to Mapper tab
3. Scroll up and down through 2D Room Map Symbol font list
4. Observe crash?

Error output / Expected result of feature

Extra information, such as Mudlet version, operating system and ideas for how to solve / implement:

Windows 10 home, Mudlet 3.20.1+