The exceptions of nullable field

Many field are nullable, but use !! in the calling place, which is very unsafe and easily lead to exceptions or crashes. such as:

W/System.err: java.lang.NullPointerException
W/System.err: at com.dragonbones.animation.AnimationState.getAnimationData(AnimationState.kt:1501)
W/System.err: at com.dragonbones.animation.Animation.advanceTime(Animation.kt:209)
W/System.err: at com.dragonbones.armature.Armature._advanceTime(Armature.kt:338)
W/System.err: at com.dragonbones.armature.Armature.advanceTime(Armature.kt:310)
W/System.err: at com.soywiz.korge.dragonbones.KorgeDbArmatureDisplay$1.invoke-eeKXlv4(KorgeDbArmatureDisplay.kt:67)
W/System.err: at com.soywiz.korge.dragonbones.KorgeDbArmatureDisplay$1.invoke(KorgeDbArmatureDisplay.kt:64)
W/System.err: at com.soywiz.korge.view.ViewKt$addUpdater$component$1.update-_rozLdE(View.kt:1648)
W/System.err: at com.soywiz.korge.view.ViewsKt.updateSingleViewWithViewsAll-rsF1gfE(Views.kt:644)
W/System.err: at com.soywiz.korge.view.Views.update-_rozLdE(Views.kt:412)
W/System.err: at com.soywiz.korge.view.Views.frameUpdateAndRender-_rozLdE(Views.kt:400)
W/System.err: at com.soywiz.korge.Korge$prepareViewsBase$15.invoke(Korge.kt:527)
W/System.err: at com.soywiz.korge.Korge$prepareViewsBase$15.invoke(Korge.kt:518)
W/System.err: at com.soywiz.korev.EventDispatcher$Mixin.dispatch(EventDispatcher.kt:50)
W/System.err: at com.soywiz.korgw.GameWindow.dispatchRenderEvent(GameWindow.kt:985)
W/System.err: at com.soywiz.korgw.GameWindow.frameRender(GameWindow.kt:580)
W/System.err: at com.soywiz.korgw.GameWindow.frame-LZ20uQo(GameWindow.kt:550)
W/System.err: at com.soywiz.korgw.GameWindow.frame-LZ20uQo$default(GameWindow.kt:547)

The above exception has a very low probability of occurrence, and there is no recurrence path.

Start at AnimationState.kt:1501 and follow the stack through Animation.kt:209 and Armature.kt:338 to identify which nullable field reaches the unsafe call. Review the related nullable-field call sites described in the issue and reproduce the reported animation update path if possible. Done means the reported NullPointerException path is handled without unsafe nullable access.

Written by the indexing model from the issue text.