fix(miner): guard XDPoS-specific worker paths

Author: gzliudan

miner/worker.go

@@ -284,10 +284,15 @@ func (w *worker) update() {
 	defer w.chainHeadSub.Unsubscribe()
 	defer w.chainSideSub.Unsubscribe()
 
+	xdposEngine, ok := w.engine.(*XDPoS.XDPoS)
+	if !ok {
+		return
+	}
+
 	// timeout waiting for v1 initial value
 	minePeriod := 2
-	MinePeriodCh := w.engine.(*XDPoS.XDPoS).MinePeriodCh
-	NewRoundCh := w.engine.(*XDPoS.XDPoS).NewRoundCh
+	MinePeriodCh := xdposEngine.MinePeriodCh
+	NewRoundCh := xdposEngine.NewRoundCh
 
 	timeout := time.NewTimer(time.Duration(minePeriod) * time.Second)
 	defer timeout.Stop()
@@ -662,15 +667,18 @@ func (w *worker) checkPreCommitWithLock() (*types.Block, bool) {
 // checkPreCommit checks whether a new work commit is needed,
 // returns the parent block and shouldReturn.
 func (w *worker) checkPreCommit() (*types.Block, bool) {
-	c := w.engine.(*XDPoS.XDPoS)
+	var xdposEngine *XDPoS.XDPoS
+	if engine, ok := w.engine.(*XDPoS.XDPoS); ok {
+		xdposEngine = engine
+	}
 	var parent *types.Block
 	currentHeader := w.chain.CurrentBlock()
 	// Guard against nil header (early startup or uninitialised chain).
 	if currentHeader == nil {
 		return nil, true
 	}
-	if c != nil {
-		parent = c.FindParentBlockToAssign(w.chain, currentHeader)
+	if xdposEngine != nil {
+		parent = xdposEngine.FindParentBlockToAssign(w.chain, currentHeader)
 	} else {
 		parent = w.chain.GetBlock(currentHeader.Hash(), currentHeader.Number.Uint64())
 	}
@@ -687,8 +695,8 @@ func (w *worker) checkPreCommit() (*types.Block, bool) {
 	// Only try to commit new work if we are mining
 	if atomic.LoadInt32(&w.mining) == 1 {
 		// check if we are right after parent's coinbase in the list
-		if w.config.XDPoS != nil {
-			ok, err := c.YourTurn(w.chain, parent.Header(), w.coinbase)
+		if w.config.XDPoS != nil && xdposEngine != nil {
+			ok, err := xdposEngine.YourTurn(w.chain, parent.Header(), w.coinbase)
 			if err != nil {
 				log.Warn("Failed when trying to commit new work", "err", err)
 				return parent, true