cmd/utils: fix error at geth startup in --dev mode (ethereum#26550)

This fixes a regression in ethereum#26541 where we turned the miner address
being missing into a startup error. The address was not configured in
--dev mode.

cmd/utils/flags.go

@@ -1912,6 +1912,7 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *ethconfig.Config) {
 			// when we're definitely concerned with only one account.
 			passphrase = list[0]
 		}
+
 		// Unlock the developer account by local keystore.
 		var ks *keystore.KeyStore
 		if keystores := stack.AccountManager().Backends(keystore.KeyStoreType); len(keystores) > 0 {
@@ -1920,6 +1921,8 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *ethconfig.Config) {
 		if ks == nil {
 			Fatalf("Keystore is not available")
 		}
+
+		// Figure out the dev account address.
 		// setEtherbase has been called above, configuring the miner address from command line flags.
 		if cfg.Miner.Etherbase != (common.Address{}) {
 			developer = accounts.Account{Address: cfg.Miner.Etherbase}
@@ -1931,6 +1934,10 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *ethconfig.Config) {
 				Fatalf("Failed to create developer account: %v", err)
 			}
 		}
+		// Make sure the address is configured as fee recipient, otherwise
+		// the miner will fail to start.
+		cfg.Miner.Etherbase = developer.Address
+
 		if err := ks.Unlock(developer, passphrase); err != nil {
 			Fatalf("Failed to unlock developer account: %v", err)
 		}