add blank white texture

Program.cs

@@ -191,6 +191,7 @@ public class Game : GameWindow {
   static CameraInfo activeCamera = CameraInfo.NIKON_D7000;
   static int thumbnailHeight = 100;
   static int thumbnailWidth = (int) 1.0 * thumbnailHeight * activeCamera.Resolution.X / activeCamera.Resolution.Y;
+  static Texture TEXTURE_WHITE;
 
   int windowWidth;
   int windowHeight;
@@ -280,6 +281,11 @@ public class Game : GameWindow {
         textures.Add(new Texture(image));
       }
     }
+
+    // Load blank white texture.
+    Image<Rgba32> white1x1 = new Image<Rgba32>(1, 1, new Rgba32(255, 255, 255));
+    TEXTURE_WHITE = new Texture(white1x1);
+    textures.Add(TEXTURE_WHITE);  // FIXME: remove
   }
 
   protected override void OnUnload() {