[gnome-mines] Fix crash when releasing button outside minefield

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 712c6193fc36c8342d4dffba65f3f9b2f0e9d4c1
Author: Mislav Blazevic <krofnica996 gmail com>
Date:   Fri Jun 7 15:01:15 2013 +0200

    Fix crash when releasing button outside minefield
    
    https://bugzilla.gnome.org/show_bug.cgi?id=701789

 src/minefield-view.vala |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/src/minefield-view.vala b/src/minefield-view.vala
index e21c19a..c87b31a 100644
--- a/src/minefield-view.vala
+++ b/src/minefield-view.vala
@@ -748,6 +748,10 @@ public class MinefieldView : Gtk.DrawingArea
         if (!selected.is_set || keyboard_cursor.is_set)
             return false;
 
+        /* Check if the user released button outside the minefield */
+        if (!minefield.is_location(selected.x, selected.y))
+            return false;
+
         unlook ();
 
         if (minefield.is_cleared (selected.x, selected.y))