[gtk+] center box: Fix size allocation

[Matthias Clasen <matthiasc src gnome org>]

commit 8316ec85f500107eccb0de5d9d84abc6e8044e91
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat Jun 10 07:52:01 2017 -0400

    center box: Fix size allocation
    
    This missing pair of parens was causing expanding children
    to overlap.

 gtk/gtkcenterbox.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkcenterbox.c b/gtk/gtkcenterbox.c
index 390e683..f91f0d9 100644
--- a/gtk/gtkcenterbox.c
+++ b/gtk/gtkcenterbox.c
@@ -201,7 +201,7 @@ gtk_center_box_distribute (GtkCenterBox     *self,
         start_size = center_pos;
 
       if (end_expand)
-        end_size = size - center_pos + center_size;
+        end_size = size - (center_pos + center_size);
     }
   else
     {