Can't remove shortcut for external tool

TEST CASE:
1) Enable External tools plugin
2) Open 'Tools - Manage External Tools'
3) Select any tool with a shortcut (or assign a shortcut to any tool)
4) Select the shortcut filed
Result: field text is 'Type a new accelerator, or press Backspace to clear'
5) Press Backspace

Result: shortcut is not cleared
Expected: shortcut is cleared

Note, that shortcut removal works correctly in snippets

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: gedit 3.3.3-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-14.23-generic-pae 3.2.3
Uname: Linux 3.2.0-14-generic-pae i686
ApportVersion: 1.91-0ubuntu1
Architecture: i386
Date: Thu Feb 9 16:42:22 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Alpha i386 (20120201.1)
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: gedit
UpgradeStatus: No upgrade log present (probably fresh install)