Ctrl-z doesn't work on particular layer

[GoogleCodeExporter]

What steps will reproduce the problem?
1.open .ase file with several layers
2.choose layer
3.use any drawing tool
4.if bug doesn't show up, try next layer.

What is the expected output? What do you see instead?
Undo either does nothing or deletes only part of stroke. but after pressing 
button state of the file changes from "blah.ase*" to just "blah.ase" as if it 
erased changes.

What version of the product are you using? On what operating system?
v0.9.6 - beta 3, windows 7 ultimate.

*Please provide any additional information below. If the program crashed on
Windows, you can attach the aseprite-memory.dmp file generated in the same
location where aseprite.exe is.*
this bug only works with files created earlier. i tried to create new one, save 
and reload but this didn't do anything. and bug only shows up on one layer, 
working fine with others.

Original issue reported on code.google.com by wwhis...@gmail.com on 19 Mar 2014 at 1:42

[GoogleCodeExporter]

Original comment by davidcapello on 13 Apr 2014 at 11:09

• Added labels: Milestone-1.0, Version-0.9.6-beta3

[GoogleCodeExporter]

I wasn't able to reproduce this bug. Ctrl+Z works fine.

Original comment by davidcapello on 2 May 2014 at 8:29

• Changed state: WontFix