Crash when trying to draw a card from empty draw pile

[wesen1]

The game will crash when you try to draw a card from an empty draw pile while there is only one card on the discard pile. This is the error log from android studio:

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.smorgasbork.hotdeath.Card.toString(android.content.Context, boolean)' on a null object reference
at com.smorgasbork.hotdeath.Game.cardToString(Game.java:2229)
at com.smorgasbork.hotdeath.Game.advanceRound(Game.java:1015)
at com.smorgasbork.hotdeath.Game.runRound(Game.java:798)
at com.smorgasbork.hotdeath.Game.run(Game.java:823)

Another error is, that two AI players will continue playing forever if all cards are on their hands. Both errors happen because of the combination of "Mystery Wild" and "69" card (when a player has to draw 69 cards).