Fixed hint bug

Fixed a bug where the program crashed when you click hint when the board is already filled in

PuzzlePlayer/Board.cs

@@ -105,8 +105,20 @@ namespace PuzzlePlayer_Namespace
         {
             int row;
             int col;
+            bool hintPossible = false;
 
-            while (true)
+            for (int i = 0; i < boardLength; i++)
+            {
+                for (int j = 0; j < boardLength; j++)
+                {
+                    if (boardState[i, j] == emptySpace)
+                    {
+                        hintPossible = true;
+                    }
+                }
+            }
+
+            while (hintPossible)
             {
                 row = RandomNumber(boardLength) - 1;
                 col = RandomNumber(boardLength) - 1;