From 010b2e808130139d5b3608f2c023fd3a518641c6 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sun, 15 May 2011 12:35:54 -0600
Subject: [PATCH] MOBI Input: Don't error out when detecting TOC structure if
 one of the elements has an invalid margin unit

---
 src/calibre/ebooks/mobi/reader.py | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/calibre/ebooks/mobi/reader.py b/src/calibre/ebooks/mobi/reader.py
index 3d858864a8..934e8476d2 100644
--- a/src/calibre/ebooks/mobi/reader.py
+++ b/src/calibre/ebooks/mobi/reader.py
@@ -690,6 +690,14 @@ class MobiReader(object):
                 lm = unit_convert('2em', 12, 500, 166)
             lm = self.left_margins.get(tag, lm)
             ti = self.text_indents.get(tag, ti)
+            try:
+                lm = float(lm)
+            except:
+                lm = 0.0
+            try:
+                ti = float(ti)
+            except:
+                ti = 0.0
             return lm + ti
 
         parent = tag