Add conditions support to GUIImage

Signed-off-by: Vojtech Bocek <vbocek@gmail.com>
diff --git a/gui/objects.hpp b/gui/objects.hpp
index 1e272b2..c259fd4 100644
--- a/gui/objects.hpp
+++ b/gui/objects.hpp
@@ -215,7 +215,7 @@
 };
 
 // GUIImage - Used for static image
-class GUIImage : public RenderObject
+class GUIImage : public RenderObject, public Conditional
 {
 public:
 	GUIImage(xml_node<>* node);