java.lang.ArithmeticException: Division undefined
at java.math.BigDecimal.divide(Unknown Source)
at org.openstreetmap.josm.tools.Geometry.getCentroid(Geometry.java:630)
at org.openstreetmap.josm.actions.AlignInCircleAction.actionPerformed(AlignInCircleAction.java:187)
at javax.swing.SwingUtilities.notifyAction(Unknown Source)
at javax.swing.JComponent.processKeyBinding(Unknown Source)
at javax.swing.KeyboardManager.fireBinding(Unknown Source)
at javax.swing.KeyboardManager.fireKeyboardAction(Unknown Source)
at javax.swing.JComponent.processKeyBindingsForAllComponents(Unknown Source)
at javax.swing.JComponent.processKeyBindings(Unknown Source)
at javax.swing.JComponent.processKeyEvent(Unknown Source)
...
Agreed, reproduced with r5312: