InvalidCastException: Cannot cast from source type to destination type

Hi! I found an open source project on github -> MatchThree. I have seen, there is a bug. When I started to play this game, I found the mentioned bug: "If we try to switch a bomb and a figure that has a 3 match, then nothing happens. Neither the bomb does not work, nor the 3 identical figures will disappear" and got this message:

 InvalidCastException: Cannot cast from source type to destination type.
 Board+<SwitchTilesRoutine>c__Iterator0.MoveNext () (at Assets/Scripts/Board/Board.cs:272)
 UnityEngine.SetupCoroutine.InvokeMoveNext (IEnumerator enumerator, IntPtr returnValueAddress) (at C:/buildslave/unity/build/Runtime/Export/Coroutines.cs:17)
 

Can you help me to find the solution?

  IEnumerator SwitchTilesRoutine(Tile clickedTile, Tile targetTile)
     {
         if (_playerInputEnabled && !GameManager.Instance.IsGameOver)
         {
             GamePiece clickedPiece = AllPieces[clickedTile.IndexX, clickedTile.IndexY];
             GamePiece targetPiece = AllPieces[targetTile.IndexX, targetTile.IndexY];
 
             if (targetPiece != null && clickedPiece != null)
             {
                 clickedPiece.Move(targetTile.IndexX, targetTile.IndexY, _swapTime);
                 targetPiece.Move(clickedTile.IndexX, clickedTile.IndexY, _swapTime);
 
                 yield return new WaitForSeconds(_swapTime);
 
                 List<GamePiece> clickedPieceMatches = new List<GamePiece>();
                 List<GamePiece> targetPieceMatches = new List<GamePiece>();
 
                 List<GamePiece> clickedPieceBombed = new List<GamePiece>();
                 List<GamePiece> targetPieceBombed = new List<GamePiece>();
 
                 if (clickedPiece.GetType() == typeof(Bomb))
                 {
                     Bomb clickedBomb = (Bomb)clickedPiece;
                     if (clickedBomb.BombType == BombType.Color)
                     {
                         clickedBomb.MatchValue = targetPiece.MatchValue;
                     }                 
                     clickedPieceBombed = MatchFinder.FindBombedPieces(AllPieces, clickedBomb);
                 }
                     
                 else
                     clickedPieceMatches = MatchFinder.FindMatchesAt(AllPieces, clickedTile.IndexX, clickedTile.IndexY);
 
                 if (targetPiece.GetType() == typeof(Bomb))
                 {
                     Bomb targetBomb = (Bomb)clickedPiece; //the problem
                     if (targetBomb.BombType == BombType.Color)
                     {
                         targetBomb.MatchValue = clickedPiece.MatchValue;
                     }
                     clickedPieceBombed = MatchFinder.FindBombedPieces(AllPieces, targetBomb);
                 }
                 else
                     targetPieceMatches = MatchFinder.FindMatchesAt(AllPieces, targetTile.IndexX, targetTile.IndexY);
 
                 if (targetPieceMatches.Count == 0 && clickedPieceMatches.Count == 0
                     && targetPieceBombed.Count == 0 && clickedPieceBombed.Count == 0)
                 {
                     clickedPiece.Move(clickedTile.IndexX, clickedTile.IndexY, _swapTime);
                     targetPiece.Move(targetTile.IndexX, targetTile.IndexY, _swapTime);
                 }
                 else
                 {
                     if (GameManager.Instance != null)
                     {
                         GameManager.Instance.UpdateMoves();
                     }
 
                     Vector2 swipeDirection = new Vector2(targetTile.IndexX - clickedTile.IndexX, targetTile.IndexY - clickedTile.IndexY);
 
                     _clickedTileBomb = DropBomb(clickedTile.IndexX, clickedTile.IndexY, swipeDirection, clickedPieceMatches);
                     _targetTileBomb = DropBomb(targetTile.IndexX, targetTile.IndexY, swipeDirection, targetPieceMatches);
 
                     ClearAndRefillBoard(clickedPieceMatches.Union(targetPieceMatches).ToList()
                         .Union(targetPieceBombed).ToList().Union(clickedPieceBombed).ToList());
                 }
             }
         }
 
     }