Steps to reproduce:

1. Open attached project
2. Make sure that Sprite Packer is enabled (Editor Settings)
3. Try to build the project using 'Build & Run' for iOS/AppleTV/Android (standalone won't work)
4. Editor will crash during the build

Note:
Like mentioned above, standalone player builds fine, however, iOS/AppleTV/Android causes the editor to crash. Likely to be observed on other platforms, haven't checked.
Disabling Sprite Packer prevents the crash.
Using just 'Build' also prevents the crash.
Issue also occurs with Legacy Sprite Packer if user assigns a tag to a sprite and presses Build & Run before pressing Play/Pack (ie. the user is forcing the sprite packer to pack only at the point of deployment, which should force a progress bar to display)

Occurring on: macOS 10.12.4, 10.12.2
Not occurring: OSX 10.11.2

Reproduced with: 2017.1.0b2, 2017.1.0b3
Couldn't check with 2017.1.0b1 due to other bug that prevents using 'Build & Run' at all
Did not reproduce on: 2017.1.0a1