Fix some possible null reference exceptions

osu.Game/Screens/Select/Leaderboards/DrawableRank.cs

@@ -46,7 +46,9 @@ private void load(TextureStore textures)
         public void UpdateRank(ScoreRank newRank)
         {
             Rank = newRank;
-            updateTexture();
+
+            if (IsLoaded)
+                updateTexture();
         }
     }
 }

osu.Game/Users/Country.cs

@@ -42,7 +42,9 @@ public Country Country
                     return;
 
                 country = value;
-                sprite.Texture = getFlagTexture();
+
+                if (IsLoaded)
+                    sprite.Texture = getFlagTexture();
             }
         }