[gnumeric] XLS: Fix problem with name referencing deleted sheet.

[Morten Welinder <mortenw src gnome org>]

commit c8c1eb346b7c8eaccf9a17efc117fee51ab80ed0
Author: Morten Welinder <terra gnome org>
Date:   Sat Oct 17 14:51:40 2015 -0400

    XLS: Fix problem with name referencing deleted sheet.

 NEWS                            |    1 +
 plugins/excel/ChangeLog         |    4 ++++
 plugins/excel/ms-formula-read.c |    4 ++++
 3 files changed, 9 insertions(+), 0 deletions(-)
---
diff --git a/NEWS b/NEWS
index de00493..875fc02 100644
--- a/NEWS
+++ b/NEWS
@@ -2,6 +2,7 @@ Gnumeric 1.12.25
 
 Morten:
        * Fix TABLE problems.  [#752181]  [#752178]
+       * Fuzzed file fixes.  [#752179]
 
 --------------------------------------------------------------------------
 Gnumeric 1.12.24
diff --git a/plugins/excel/ChangeLog b/plugins/excel/ChangeLog
index df56231..25ff96c 100644
--- a/plugins/excel/ChangeLog
+++ b/plugins/excel/ChangeLog
@@ -1,3 +1,7 @@
+2015-10-17  Morten Welinder  <terra gnome org>
+
+       * ms-formula-read.c (excel_parse_formula1): Handle deleted sheet.
+
 2015-09-20  Morten Welinder <terra gnome org>
 
        * Release 1.12.24
diff --git a/plugins/excel/ms-formula-read.c b/plugins/excel/ms-formula-read.c
index 3494a93..f9112f0 100644
--- a/plugins/excel/ms-formula-read.c
+++ b/plugins/excel/ms-formula-read.c
@@ -1756,7 +1756,11 @@ excel_parse_formula1 (MSContainer const *container,
                                        sheet = nexpr->pos.sheet;
                                        if (sheet == NULL)
                                                sheet = ms_container_sheet (container);
+                               } else if (sheet == XL_EXTERNSHEET_MAGIC_DELETED) {
+                                       /* What?  Happens for #752179.  */
+                                       sheet = NULL;
                                }
+
                                name = gnm_expr_new_name (nexpr, sheet, NULL);
                        }