Fix tapping on opponent's piece

With the previous change of starting a tap on a drag,
we removed the GestureDetector from all squares with any pieces.

This included the opponent's pieces. Tapping and taking an opponent's
piece was not possible anymore.

This was a bug, since we still want to detect a tap and take an opponent's piece.

lib/chess/chess_square.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:mchess/chess/chess_square_outer_dragtarget.dart';
+import 'package:mchess/chess_bloc/chess_bloc.dart';
 import 'package:mchess/chess_bloc/tap_bloc.dart';
 import '../utils/chess_utils.dart';
 
@@ -66,7 +67,8 @@ class _ChessSquareState extends State<ChessSquare> {
           containedPiece: widget.containedPiece ?? const ChessPiece.none()),
     );
 
-    if (widget.containedPiece == null) {
+    if (widget.containedPiece == null ||
+        widget.containedPiece!.color != ChessBloc.getMyColor()) {
       return GestureDetector(
         child: dragTarget,
         onTap: () {

lib/chess/chess_square_outer_dragtarget.dart

@@ -30,13 +30,13 @@ class ChessSquareOuterDragTarget extends StatelessWidget {
 
         if (isPromotionMove(
           details.data.movedPiece!.pieceClass,
-          ChessBloc.myColor!,
+          ChessBloc.getMyColor(),
           details.data.toSquare,
         )) {
           var move = ChessMove(
               from: details.data.fromSquare, to: details.data.toSquare);
           PromotionBloc().add(PawnMovedToPromotionField(
-              move: move, colorMoved: ChessBloc.myColor!));
+              move: move, colorMoved: ChessBloc.myColor));
         } else if (coordinate != details.data.fromSquare) {
           ChessBloc().add(OwnPieceMoved(
               startSquare: details.data.fromSquare,

lib/chess_bloc/chess_bloc.dart

@@ -11,9 +11,9 @@ import 'package:mchess/utils/chess_utils.dart';
 class ChessBloc extends Bloc<ChessEvent, ChessBoardState> {
   static final ChessBloc _instance = ChessBloc._internal();
   static ChessColor turnColor = ChessColor.white;
-  static ChessColor? myColor = ChessColor.white;
+  static ChessColor myColor = ChessColor.white;
 
-  static ChessColor? getSidesColor() {
+  static ChessColor getMyColor() {
     return myColor;
   }
 
@@ -126,7 +126,7 @@ class ChessBloc extends Bloc<ChessEvent, ChessBoardState> {
       OwnPromotionPlayed event, Emitter<ChessBoardState> emit) {
     var apiMove = event.move.toApiMove();
     var shorNameForPiece = chessPiecesShortName[
-        ChessPieceAssetKey(pieceClass: event.pieceClass, color: myColor!)]!;
+        ChessPieceAssetKey(pieceClass: event.pieceClass, color: myColor)]!;
     apiMove.promotionToPiece = shorNameForPiece;
     var message = ApiWebsocketMessage(
       type: MessageType.move,

lib/chess_bloc/tap_bloc.dart

@@ -51,12 +51,12 @@ class TapBloc extends Bloc<TapEvent, TapState> {
         state.firstSquareTapped != event.tapped) {
       if (isPromotionMove(
         state.pieceOnFirstTappedSquare!.pieceClass,
-        ChessBloc.myColor!,
+        ChessBloc.myColor,
         event.tapped,
       )) {
         PromotionBloc().add(PawnMovedToPromotionField(
             move: ChessMove(from: state.firstSquareTapped!, to: event.tapped),
-            colorMoved: ChessBloc.myColor!));
+            colorMoved: ChessBloc.myColor));
         emit(TapState.init());
         return;
       } else {

lib/pages/lobby_selector.dart

@@ -168,8 +168,10 @@ class _LobbySelectorState extends State<LobbySelector> {
         backgroundColor: Colors.amberAccent,
         content: Text("mChess server is not responding. Try again or give up"),
       );
-      ScaffoldMessenger.of(context).clearSnackBars();
-      ScaffoldMessenger.of(context).showSnackBar(snackBar);
+      if (mounted) {
+        ScaffoldMessenger.of(context).clearSnackBars();
+        ScaffoldMessenger.of(context).showSnackBar(snackBar);
+      }
       return null;
     }