From f00f89c37f7eeeadf3069565705a15085e0bb3a4 Mon Sep 17 00:00:00 2001
From: "Ben J. Woodcroft" <donttrustben near gmail.com>
Date: Sat, 22 Mar 2014 09:08:12 +1000
Subject: [PATCH] minor bugfix

---
 lib/bio-velvet/graph.rb | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/bio-velvet/graph.rb b/lib/bio-velvet/graph.rb
index 658e831..7a3e3a5 100644
--- a/lib/bio-velvet/graph.rb
+++ b/lib/bio-velvet/graph.rb
@@ -571,6 +571,10 @@ class NodedRead
       def self.apply_grep_hack(graph, path_to_graph_file, interesting_read_ids, interesting_node_ids, grep_context)
         interesting_read_ids ||= []
         interesting_node_ids ||= []
+        if interesting_read_ids.empty? and interesting_node_ids.empty?
+          log.debug "Nothing to grep for in grep hack" if log.debug?
+          return
+        end
 
         Tempfile.open('grep_v_hack') do |tempfile|
           # Create a file to pass to grep -f