[gtk+] box gadget: Deal with optional arguments

[Matthias Clasen <matthiasc src gnome org>]

commit 9c3907dab016d9c1477f2bcd1bd64a6452fd3f78
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Jan 17 19:48:40 2016 -0500

    box gadget: Deal with optional arguments
    
    The baseline arguments to the preferred size callback can
    be NULL. Don't crash if they are.

 gtk/gtkboxgadget.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkboxgadget.c b/gtk/gtkboxgadget.c
index e02c8e3..f62b0d7 100644
--- a/gtk/gtkboxgadget.c
+++ b/gtk/gtkboxgadget.c
@@ -238,8 +238,10 @@ gtk_box_gadget_measure_opposite (GtkCssGadget   *gadget,
       total_min = MAX (total_min, above_min + below_min);
       total_nat = MAX (total_nat, above_nat + below_nat);
       /* assume GTK_BASELINE_POSITION_CENTER for now */
-      *minimum_baseline = above_min + (total_min - (above_min + below_min)) / 2;
-      *natural_baseline = above_nat + (total_nat - (above_nat + below_nat)) / 2;
+      if (minimum_baseline)
+        *minimum_baseline = above_min + (total_min - (above_min + below_min)) / 2;
+      if (natural_baseline)
+        *natural_baseline = above_nat + (total_nat - (above_nat + below_nat)) / 2;
     }
 
   *minimum = total_min;