Dragging overview window on wrapped alignment in applet throws exceptions

Noticed while testing on JAL-2630 branch. Open a wrapped alignment in the applet (e.g. JalviewLite with Features) and open the overview window. Drag the overview window box - NPEs are thrown:

Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
at jalview.appletgui.AnnotationPanel.fastPaint(AnnotationPanel.java:645)
at jalview.appletgui.AnnotationPanel.propertyChange(AnnotationPanel.java:771)
at java.beans.PropertyChangeSupport.fire(PropertyChangeSupport.java:335)
at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:327)
at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:263)
at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:283)
at jalview.viewmodel.ViewportRanges.setStartEndRes(ViewportRanges.java:166)
at jalview.viewmodel.ViewportRanges.setStartRes(ViewportRanges.java:118)
at jalview.viewmodel.OverviewDimensionsShowHidden.updateViewportFromMouse(OverviewDimensionsShowHidden.java:164)
at jalview.appletgui.OverviewPanel.mouseAction(OverviewPanel.java:152)
at jalview.appletgui.OverviewPanel.mouseDragged(OverviewPanel.java:138)
at java.awt.Component.processMouseMotionEvent(Component.java:6581)
at java.awt.Component.processEvent(Component.java:6302)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4889)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:731)
at java.awt.EventQueue$4.run(EventQueue.java:729)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)