[gnumeric] Fuzzed file fix. [#751758]

[Jean Bréfort <jbrefort src gnome org>]

commit fe51b97ed54d42dbe102edac02865f0ad7a61cc3
Author: Jean Brefort <jean brefort normalesup org>
Date:   Sun Jun 28 09:07:41 2015 +0200

    Fuzzed file fix. [#751758]

 NEWS                     |    2 +-
 plugins/excel/ChangeLog  |    4 ++++
 plugins/excel/ms-chart.c |   20 +++++++++++---------
 3 files changed, 16 insertions(+), 10 deletions(-)
---
diff --git a/NEWS b/NEWS
index 0ee5c8c..4db938d 100644
--- a/NEWS
+++ b/NEWS
@@ -15,7 +15,7 @@ Jean:
        * Fix xlsx import of plot area manual layout. [#748016]
        * Fix out of bounds read. [#749121]
        * Fuzzed file fixes.  [#750042] [#751217] [#751270] [#751271]
-          [#751383] [#751384]
+          [#751383] [#751384] [#751758]
 
 Morten:
        * Fix import/export of graph backplane.
diff --git a/plugins/excel/ChangeLog b/plugins/excel/ChangeLog
index 982c85b..6771319 100644
--- a/plugins/excel/ChangeLog
+++ b/plugins/excel/ChangeLog
@@ -1,3 +1,7 @@
+2015-06-28  Jean Brefort  <jean brefort normalesup org>
+
+       * ms-chart.c (end): fuzzed file fix. [#751758]
+
 2015-06-25  Jean Brefort  <jean brefort normalesup org>
 
        * ms-chart.c (end): more unexisting series issues. See #751270, comment #2
diff --git a/plugins/excel/ms-chart.c b/plugins/excel/ms-chart.c
index 6bd1ba1..06afc69 100644
--- a/plugins/excel/ms-chart.c
+++ b/plugins/excel/ms-chart.c
@@ -3215,15 +3215,17 @@ not_a_matrix:
        }
 
        case BIFF_CHART_dropbar :
-               if (s->dropbar_style == NULL) {
-                       /* automatic styles are very different in that case between
-                       excel and gnumeric, so set appropriate auto* to FALSE */
-                       s->style->fill.auto_back = FALSE;
-                       s->style->fill.auto_fore = FALSE;
-                       s->dropbar_style = s->style;
-               } else
-               g_object_unref (s->style);
-               s->style = NULL;
+               if (s->style != NULL) {
+                       if (s->dropbar_style == NULL) {
+                               /* automatic styles are very different in that case between
+                               excel and gnumeric, so set appropriate auto* to FALSE */
+                               s->style->fill.auto_back = FALSE;
+                               s->style->fill.auto_fore = FALSE;
+                               s->dropbar_style = s->style;
+                       } else
+                               g_object_unref (s->style);
+                       s->style = NULL;
+               }
                break;
 
        case BIFF_CHART_chart : {