[goffice] Fix crash in 3D plots when X or Y values are missing. [#788437]

[Jean Bréfort <jbrefort src gnome org>]

commit 63aff6ab8e6d335d8879731adf372cac5e03c911
Author: Jean Brefort <jean brefort normalesup org>
Date:   Mon Oct 2 19:04:42 2017 +0200

    Fix crash in 3D plots when X or Y values are missing. [#788437]

 ChangeLog                              |    6 ++++++
 NEWS                                   |    1 +
 plugins/plot_surface/gog-xyz-surface.c |    2 ++
 3 files changed, 9 insertions(+), 0 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index dff7c42..deffcf4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2017-10-02  Jean Brefort  <jean brefort normalesup org>
+
+       * plugins/plot_surface/gog-xyz-surface.c
+       (gog_xyz_surface_plot_build_matrix): don't crash if X or Y values are
+       missing. [#788437]
+
 2017-08-03  Jean Brefort  <jean brefort normalesup org>
 
        * goffice/utils/go-format.c (printf_engineering): fix engineering format.
diff --git a/NEWS b/NEWS
index 4d0caaf..f332655 100644
--- a/NEWS
+++ b/NEWS
@@ -2,6 +2,7 @@ goffice 0.10.36:
 
 Jean:
        * Fix engineering format. [#785669]
+       * Fix crash in 3D plots when X or Y values are missing. [#788437]
 
 --------------------------------------------------------------------------
 goffice 0.10.35:
diff --git a/plugins/plot_surface/gog-xyz-surface.c b/plugins/plot_surface/gog-xyz-surface.c
index 53d373a..b1a1750 100644
--- a/plugins/plot_surface/gog-xyz-surface.c
+++ b/plugins/plot_surface/gog-xyz-surface.c
@@ -325,6 +325,8 @@ gog_xyz_surface_plot_build_matrix (GogXYZPlot *plot, gboolean *cardinality_chang
                                                         &x_vals, &y_vals, &z_vals);
        else
                kmax = gog_series_get_xy_data (GOG_SERIES (series), &x_vals, &y_vals);
+       if (x_vals == NULL || y_vals == NULL)
+               return NULL;
        /* sort the data by column and row */
        raw_data.values[0] = x_vals;
        raw_data.values[1] = y_vals;