Check on vscrollMax values

diff --git a/src/jalview/appletgui/AlignmentPanel.java b/src/jalview/appletgui/AlignmentPanel.java
index bcdffa0..da55119 100755 (executable)
--- a/src/jalview/appletgui/AlignmentPanel.java
+++ b/src/jalview/appletgui/AlignmentPanel.java
@@ -489,13 +489,16 @@ public class AlignmentPanel extends Panel implements AdjustmentListener
       if (av.hasHiddenColumns)\r
         maxwidth = av.getColumnSelection().findColumnPosition(maxwidth) - 1;\r
 \r
-      int max = maxwidth /\r
-          seqPanel.seqCanvas.getWrappedCanvasWidth(seqPanel.seqCanvas.getSize().width) +\r
-          1;\r
+      int canvasWidth = seqPanel.seqCanvas.getWrappedCanvasWidth\r
+          (seqPanel.seqCanvas.getSize().width);\r
 \r
-      vscroll.setMaximum(max);\r
-      vscroll.setUnitIncrement(1);\r
-      vscroll.setVisibleAmount(1);\r
+      if(canvasWidth>0)\r
+      {\r
+        int max = maxwidth / canvasWidth;\r
+        vscroll.setMaximum(max);\r
+        vscroll.setUnitIncrement(1);\r
+        vscroll.setVisibleAmount(1);\r
+      }\r
     }\r
     else\r
     {\r