Fix get() method in GomokuBoard and save() method in GomokuGame

src/GomokuBoard.java

@@ -129,6 +129,8 @@ public class GomokuBoard{
      * @return GomokuCell in the position.
      */
     public GomokuCell get(int x, int y){
+        if (x < 0 || x >= this.boardWidth) return null;
+        if (y < 0 || y >= this.boardHeight) return null;
         int i = 0, j = 0;
         GomokuCell act = this.firstCell;
         while (i != x || j != y){

src/GomokuGame.java

@@ -147,13 +147,13 @@ public class GomokuGame {
             // Write the board
             for (int i = 0; i < this.getBoard().getHeight(); ++i) {
                 for (int j = 0; j < this.getBoard().getWidth(); ++j) {
-                    char c = ' ';
+                    char c;
                     switch (board.get(i, j).getState()) {
                         case BLACK:
                             c = 'X';
                             break;
                         case WHITE:
-
+                            c = 'O';
                             break;
                         case NIL:
                             c = '.';