If groups doesnt contain group, addition is allowed

diff --git a/src/jalview/datamodel/Alignment.java b/src/jalview/datamodel/Alignment.java
index abc7cf6..e329cc8 100755 (executable)
--- a/src/jalview/datamodel/Alignment.java
+++ b/src/jalview/datamodel/Alignment.java
@@ -342,7 +342,8 @@ public class Alignment implements AlignmentI
 \r
   /**    */\r
   public void addGroup(SequenceGroup sg) {\r
-    groups.addElement(sg);\r
+    if(!groups.contains(sg))\r
+      groups.addElement(sg);\r
   }\r
 \r
   /**    */\r