[gnome-mines] Fixed preview minefield after commit revert

[Robert Roth <robertroth src gnome org>]

commit 0bb71132abf3bbd8af79be2f87ac955d948d8512
Author: Robert Roth <robert roth off gmail com>
Date:   Wed Jan 14 09:18:30 2015 +0200

    Fixed preview minefield after commit revert

 src/minefield.vala             |    2 +-
 src/theme-selector-dialog.vala |    1 +
 2 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/src/minefield.vala b/src/minefield.vala
index 9496ef7..81e2046 100644
--- a/src/minefield.vala
+++ b/src/minefield.vala
@@ -61,7 +61,7 @@ public class Minefield : Object
     public bool exploded = false;
 
     /* true if have placed the mines onto the map */
-    private bool placed_mines = false;
+    protected bool placed_mines = false;
 
     /* keep track of flags and cleared squares */
     private uint _n_cleared = 0;
diff --git a/src/theme-selector-dialog.vala b/src/theme-selector-dialog.vala
index 9211618..6b5f47f 100644
--- a/src/theme-selector-dialog.vala
+++ b/src/theme-selector-dialog.vala
@@ -5,6 +5,7 @@ private class PreviewField : Minefield
         base (7, 7, 20);
 
         place_mines (0, 0);
+        placed_mines = true;
     }
 
     protected new void place_mines (uint x, uint y)