From ec59a9b62431f6e2148c0a5f5bfc2313dd0f03b0 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Mon, 28 Sep 2020 08:45:06 +0530
Subject: [PATCH] PDF Output: Dont fail if the input document has an html file
 identified as the cover

---
 src/calibre/ebooks/conversion/plugins/pdf_output.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/calibre/ebooks/conversion/plugins/pdf_output.py b/src/calibre/ebooks/conversion/plugins/pdf_output.py
index cb26fd0b18..09ba4c77fd 100644
--- a/src/calibre/ebooks/conversion/plugins/pdf_output.py
+++ b/src/calibre/ebooks/conversion/plugins/pdf_output.py
@@ -196,7 +196,8 @@ class PDFOutput(OutputFormatPlugin):
         if (oeb.metadata.cover and unicode_type(oeb.metadata.cover[0]) in oeb.manifest.ids):
             cover_id = unicode_type(oeb.metadata.cover[0])
             item = oeb.manifest.ids[cover_id]
-            self.cover_data = item.data
+            if isinstance(item.data, bytes):
+                self.cover_data = item.data
 
     def process_fonts(self):
         ''' Make sure all fonts are embeddable '''