Twilight Struggle Module v 3.2, using Vassal 3.7.13 (Windows x64).
The error came up while hovering cards in US hand (before showing the zoomed card).
Twilight Struggle 3.1 v3.2 3.7.13
java.lang.NullPointerException: Cannot invoke "VASSAL.counters.GamePiece.getShape()" because "piece" is null
at VASSAL.build.module.map.CounterDetailViewer.getBounds(CounterDetailViewer.java:814)
at VASSAL.build.module.map.CounterDetailViewer.fixBounds(CounterDetailViewer.java:663)
at VASSAL.build.module.map.CounterDetailViewer.drawGraphics(CounterDetailViewer.java:375)
at ca.mkiefte.CardZoomer.drawGraphics(CardZoomer.java:53)