Changing side counts on round brushes causes CTD

[nukeandbeans]

Steps to reproduce:

• Create any round brush (sphere, cylinder, capsule, etc.)
• Set its side count by rapidly changing it from a small value to large value or a large value to a small value (even going from 12 to 32 will work)

Doing the above will cause unity to CTD with no error message or crash report. Doing the above and setting a side count below 3 will also cause a CTD or freeze. (fixed with #195)