From cdb2107c4e1fbae8672fd9f1aa89d2eb24cb67d2 Mon Sep 17 00:00:00 2001
From: "James R. Barlow" <jim@purplerock.ca>
Date: Wed, 18 Apr 2018 01:31:35 -0700
Subject: [PATCH] optimize: jbigs2 fix

---
 src/ocrmypdf/_optimize.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/ocrmypdf/_optimize.py b/src/ocrmypdf/_optimize.py
index f9cc9f92..346e3698 100644
--- a/src/ocrmypdf/_optimize.py
+++ b/src/ocrmypdf/_optimize.py
@@ -182,6 +182,8 @@ def convert_to_jbig2(pike, jbig2_groups, root, log, options):
             max_workers=options.jobs) as executor:
         futures = []
         for group, xrefs in jbig2_groups.items():
+            if len(xrefs) == 0:
+                continue
             prefix = 'group{:08d}'.format(group)
             cmd = ['jbig2', '-b', prefix, '-s', '-p']
             cmd.extend(make_img_name(root, xref) for xref in xrefs)