Fixed a bug that would prevent errors from being highlighted.

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/SudokuFieldLayout.java

@@ -207,13 +207,13 @@ public class SudokuFieldLayout extends RelativeLayout implements IHighlightChang
                 gamecells[i][j].invalidate();
             }
         }
+        this.invalidate();
     }
 
     @Override
     public void dispatchDraw(Canvas canvas) {
         super.dispatchDraw(canvas);
 
-
         if(gameController == null) {
             return;
         }