Fixed shop buying/selling not working

TODO.md

@@ -13,7 +13,6 @@ Map/story
 ---------
 
 * Add sound effects and more visual effects (jumps...)
-* Fix quickly zooming in twice preventing to display some UI parts
 * Add factions and reputation
 * Allow to cancel secondary missions
 * Forbid to end up with more than 5 ships in the fleet because of escorts

src/core/Shop.ts

@@ -31,6 +31,11 @@ module TK.SpaceTac {
             this.onchange = onchange || (stock => stock);
         }
 
+        postUnserialize() {
+            // functions are not serializable
+            this.onchange = (stock => stock);
+        }
+
         /**
          * Get available stock to display (sorted by level then price by default)
          */