Ensure that we set gas limit if migrating at pre-gingerbread point

op-chain-ops/cmd/celo-migrate/state.go

@@ -121,7 +121,11 @@ func applyStateMigrationChanges(config *genesis.DeployConfig, genesis *core.Gene
 	if header.BaseFee != nil {
 		baseFee = header.BaseFee
 	}
-
+	// If gas limit was zero at the transition point use a default of 30M.
+	gasLimit := header.GasLimit
+	if gasLimit == 0 {
+		gasLimit = 30e6
+	}
 	// Create the header for the Cel2 transition block.
 	cel2Header := &types.Header{
 		ParentHash:       header.Hash(),
@@ -133,7 +137,7 @@ func applyStateMigrationChanges(config *genesis.DeployConfig, genesis *core.Gene
 		Bloom:            types.Bloom{},
 		Difficulty:       new(big.Int).Set(common.Big0),
 		Number:           migrationBlock,
-		GasLimit:         header.GasLimit,
+		GasLimit:         gasLimit,
 		GasUsed:          0,
 		Time:             header.Time + 5,
 		Extra:            []byte("CeL2 migration"),