Index: trunk/src/org/openstreetmap/josm/gui/layer/gpx/GpxDrawHelper.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/layer/gpx/GpxDrawHelper.java	(revision 18252)
+++ trunk/src/org/openstreetmap/josm/gui/layer/gpx/GpxDrawHelper.java	(revision 18253)
@@ -1085,5 +1085,5 @@
 
         // select by index
-        if (tableIdx < lut.length) {
+        if (tableIdx >= 0 && tableIdx < lut.length) {
             nextUserColor = lut[ tableIdx ];
         }