From 90c62d93ed800e129d5340f999008bc7d41ba965 Mon Sep 17 00:00:00 2001
From: Jeremy Goecks <jeremy.goecks@emory.edu>
Date: Sun, 5 Feb 2012 12:53:23 -0500
Subject: [PATCH] Handle instance where BAMDataProvider iterator is None; this
 can occur when trying to fetch additional data.

---
 lib/galaxy/visualization/tracks/data_providers.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/galaxy/visualization/tracks/data_providers.py b/lib/galaxy/visualization/tracks/data_providers.py
index de0ed94057a..1cc8196105e 100644
--- a/lib/galaxy/visualization/tracks/data_providers.py
+++ b/lib/galaxy/visualization/tracks/data_providers.py
@@ -646,6 +646,10 @@ class BamDataProvider( TracksDataProvider ):
             max_high - highest coordinate for the returned reads
             message - error/informative message
         """
+        # No iterator indicates no reads.
+        if iterator is None:
+            return { 'data': [], 'message': None }
+        
         # Decode strand from read flag.
         def decode_strand( read_flag, mask ):
             strand_flag = ( read_flag & mask == 0 )