[gnumeric] xls: improve handling of broken files.

[Morten Welinder <mortenw src gnome org>]

commit d0fac97acae7e98bffcac713bfc7d30c3a7ca4b5
Author: Morten Welinder <terra gnome org>
Date:   Sat Apr 20 15:47:52 2013 -0400

    xls: improve handling of broken files.

 plugins/excel/ChangeLog       | 1 +
 plugins/excel/ms-excel-read.c | 1 +
 2 files changed, 2 insertions(+)
---
diff --git a/plugins/excel/ChangeLog b/plugins/excel/ChangeLog
index 22c2502..d2ee37d 100644
--- a/plugins/excel/ChangeLog
+++ b/plugins/excel/ChangeLog
@@ -3,6 +3,7 @@
        * ms-excel-read.c (excel_read_name_str): Make sure we don't end up
        requesting (size_t)-1 characters worth of data.  Fixes #698424,
        initial item.
+       (ms_wb_parse_expr): NULL the dummy container vtable.
 
 2013-04-15  Morten Welinder  <terra gnome org>
 
diff --git a/plugins/excel/ms-excel-read.c b/plugins/excel/ms-excel-read.c
index a01997c..cc5b939 100644
--- a/plugins/excel/ms-excel-read.c
+++ b/plugins/excel/ms-excel-read.c
@@ -3210,6 +3210,7 @@ ms_wb_parse_expr (MSContainer *container, guint8 const *data, int length)
 {
        ExcelReadSheet dummy_sheet;
 
+       dummy_sheet.container.vtbl = NULL;
        dummy_sheet.container.importer = (GnmXLImporter *)container;
        dummy_sheet.sheet = NULL;
        dummy_sheet.shared_formulae = NULL;