Delayed dialog removal is not thread safe.

[jdngray77]

feedback 23

Concurrent modification of docked windows causes a crash.

Exception in thread "Thread-2" java.lang.IndexOutOfBoundsException: index can't be >= size: 11 >= 11
        at com.badlogic.gdx.utils.Array.removeIndex(Array.java:290)
        at com.badlogic.gdx.utils.SnapshotArray.removeIndex(SnapshotArray.java:138)
        at com.badlogic.gdx.utils.Array.removeValue(Array.java:273)
        at com.badlogic.gdx.utils.SnapshotArray.removeValue(SnapshotArray.java:133)
        at com.shinkson47.SplashX6.rendering.StageWindow.unPost(StageWindow.java:130)
        at com.shinkson47.SplashX6.rendering.StageWindow.clear(StageWindow.java:667)
        at com.shinkson47.SplashX6.rendering.windows.MessageWindow$closer._init_$lambda-0(MessageWindow.kt:26)
        at java.base/java.lang.Thread.run(Thread.java:833)
Exception in thread "LWJGL Application" java.util.ConcurrentModificationException
        at java.base/java.util.ArrayList$Itr.checkForComodification(ArrayList.java:1013)
        at java.base/java.util.ArrayList$Itr.next(ArrayList.java:967)
        at com.shinkson47.SplashX6.game.GameHypervisor$Companion.doEndTurn_Async(GameHypervisor.kt:732)
        at com.shinkson47.SplashX6.game.GameHypervisor$Companion.turn_end(GameHypervisor.kt:407)
        at com.shinkson47.SplashX6.input.KeyBinder.lambda-14$lambda-12(KeyBinder.kt:123)
        at com.shinkson47.SplashX6.input.KeyBinder$MatchAndExecute$1.invoke(KeyBinder.kt:256)
        at com.shinkson47.SplashX6.input.KeyBinder$MatchAndExecute$1.invoke(KeyBinder.kt:256)
        at com.shinkson47.SplashX6.input.KeyBinder.poll(KeyBinder.kt:247)
        at com.shinkson47.SplashX6.input.KeyBinder.keyDown(KeyBinder.kt:261)
        at com.badlogic.gdx.InputMultiplexer.keyDown(InputMultiplexer.java:80)
        at com.badlogic.gdx.InputEventQueue.drain(InputEventQueue.java:58)
        at com.badlogic.gdx.backends.lwjgl.DefaultLwjglInput.processEvents(DefaultLwjglInput.java:255)
        at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:220)
        at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:127)