Hey, I browsed the forums for a related issue, and found someone having the same issue (http://esotericsoftware.com/forum/viewtopic.php?f=9&t=2499&p=12149&hilit=duplicate#p12149). However, in the reply Nate responded that there is no issue with 1.8.28. I'm using the latest (1.8.39) so I'm not sure if that issue was really resolved.
Steps to Reproduce:
1) Clicking the [Duplicate Animation] button.
Lately I've been updating Spline every time it offers, but I never had this problem and this has been the only time its crashed (that button worked in older Spine versions). Is there a recommended stable version I should just stick with for my particular machine? Here is the log file to try to help you.
Spine Launcher 1.8.14-full
Mac OS X x86_64 10.9.2
Java 1.7.0_51 Oracle Corporation
Java HotSpot(TM) 64-Bit Server VM
Up to date: 1.8.39
Spine 1.8.39 Essential, JGLFW
ATI Technologies Inc.
AMD Radeon HD 6750M OpenGL Engine
2.1 ATI-1.20.11
Using customized hotkeys.
Started.
An unexpected error has occurred:
java.lang.RuntimeException
at wT.a(SourceFile:51)
at wT.<init>(SourceFile:47)
at lQ.J(SourceFile:1468)
at mL.a(SourceFile:1939)
at eQ.a(SourceFile:28)
at dv.a(SourceFile:166)
at dv.a(SourceFile:131)
at com.badlogic.gdx.scenes.scene2d.ui.Button.c(SourceFile:112)
at dX.b(SourceFile:86)
at eS.b(SourceFile:89)
at dB.a(SourceFile:57)
at dD.b(SourceFile:272)
at o.b(SourceFile:94)
at aq.b(SourceFile:86)
at q.a(SourceFile:80)
at ap.d(SourceFile:124)
at ac.e(SourceFile:210)
at kJ.e(SourceFile:98)
at ah.run(SourceFile:188)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:733)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:703)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)