eth/tracers: fix nil pointer dereference in TraceCall with BlockOverrides

Author: hero5512

eth/tracers/api.go

@@ -959,7 +959,7 @@ func (api *API) TraceCall(ctx context.Context, args ethapi.TransactionArgs, bloc
 
 	// Apply the customization rules if required.
 	if config != nil {
-		if config.BlockOverrides != nil && config.BlockOverrides.Number.ToInt().Uint64() == h.Number.Uint64()+1 {
+		if config.BlockOverrides != nil && config.BlockOverrides.Number != nil && config.BlockOverrides.Number.ToInt().Uint64() == h.Number.Uint64()+1 {
 			// Overriding the block number to n+1 is a common way for wallets to
 			// simulate transactions, however without the following fix, a contract
 			// can assert it is being simulated by checking if blockhash(n) == 0x0 and