no action if supplied colour isnull

diff --git a/src/jalview/gui/SliderPanel.java b/src/jalview/gui/SliderPanel.java
index 79a05de..fca4105 100755 (executable)
--- a/src/jalview/gui/SliderPanel.java
+++ b/src/jalview/gui/SliderPanel.java
@@ -50,6 +50,9 @@ public class SliderPanel extends GSliderPanel
 \r
   public void valueChanged(int i)\r
   {\r
+    if(cs == null)\r
+      return;\r
+\r
     ColourSchemeI toChange = null;\r
     Vector allGroups = null;\r
     int groupIndex = 0;\r