Do not start or unpause an animation with no definition or 0 duration
Do not start or unpause an animation with no definition or 0 duration

Doing so can cause infinite loops with loop and bounce replay modes.
Reported by Jordan Weber, thanks!

OpenTechEngine/CEGUI,ruleless/CEGUI,OpenTechEngine/CEGUI,ruleless/CEGUI,OpenTechEngine/CEGUI,ruleless/CEGUI,OpenTechEngine/CEGUI,ruleless/CEGUI