duplicate filter would crash if there wre no waypoints in the list

diff --git a/duplicate.c b/duplicate.c
index 570cf370157182fa43fe9f68f04724a97548071d..15fe41ce447920b75d258e83ec27968eb083d4f4 100644 (file)
--- a/duplicate.c
+++ b/duplicate.c
@@ -273,7 +273,9 @@ duplicate_process(void)
        }
 
        xfree(htable);
-       free_tree(sup_tree);
+       if ( sup_tree ) {
+               free_tree(sup_tree);
+       }
 }
 
 void