What I expected to happen was...:
Tried to simply change the resource pack from one made by that tool to the default one.
What actually happened was...:
Minecraft crashed D:
There is the crash log attached.
Environment
OS: Windows 7 (ver 6.1, arch amd64)
Java: 1.7.0_17 (by Oracle Corporation)
Launcher: 0.9.3 (Dev) (bootstrap 3)
Minecraft: 13w24b (updated Fri Jun 14 15:54:59 CEST 2013)
Duplicate of MC-17831, please use the search function to see if your bug has already been submitted. Currently over 57% of tickets are being closed as duplicate.