To reproduce:
1. Import the Repro package
2. Open scene Castle Defense
3. Select the terrain and through the inspector navigate to the tree menu - notice it has a "Missing" tree
4. Add a new tree and select the "Dead Tree" prefab from the assets
5. Try placing and removing the dead trees - everything seems fine
6. Now remove the "Missing" tree from the terrain
7. Try placing and removing the "Dead Tree" again - an error followed by a crash:
"Runtime Error!
Program: C:\Program Files (x86)\Unity\Editor\Unity.exe
R6025
-pure virtual function call"

Version 4.2.2f1 produces glitchy trees but does not crash