Do not return the error in case if onRamp not initialized (#1487)

## Motivation
For the exec provider, in some cases, the onRamp reader is not
initialized. For immediate reaction, we need to allow execution without
blocking in cases if onRamp is not initialized. It fails due the issue
when onRampReader is not initialized for execProvider. This fix should
fix this issue. In case the onRamp reader is not initialized, the module
will return 0 values and DAGasEstimator will behave as it worked before
this feature been implemented.

core/services/ocr2/plugins/ccip/estimatorconfig/config.go

@@ -2,7 +2,6 @@ package estimatorconfig
 
 import (
 	"context"
-	"errors"
 	"math/big"
 
 	"github.com/smartcontractkit/chainlink-common/pkg/types/ccip"
@@ -42,7 +41,7 @@ func (c *FeeEstimatorConfigService) SetOnRampReader(reader ccip.OnRampReader) {
 // GetDynamicConfig should be cached in the onRamp reader to avoid unnecessary on-chain calls
 func (c *FeeEstimatorConfigService) GetDataAvailabilityConfig(ctx context.Context) (destDataAvailabilityOverheadGas, destGasPerDataAvailabilityByte, destDataAvailabilityMultiplierBps int64, err error) {
 	if c.onRampReader == nil {
-		return 0, 0, 0, errors.New("no OnRampReader has been configured")
+		return 0, 0, 0, nil
 	}
 
 	cfg, err := c.onRampReader.GetDynamicConfig(ctx)

core/services/ocr2/plugins/ccip/estimatorconfig/config_test.go

@@ -24,8 +24,11 @@ func TestFeeEstimatorConfigService(t *testing.T) {
 	var expectedDestDataAvailabilityMultiplierBps int64 = 3
 
 	onRampReader := mocks.NewOnRampReader(t)
-	_, _, _, err := svc.GetDataAvailabilityConfig(ctx)
-	require.Error(t, err)
+	destDataAvailabilityOverheadGas, destGasPerDataAvailabilityByte, destDataAvailabilityMultiplierBps, err := svc.GetDataAvailabilityConfig(ctx)
+	require.NoError(t, err) // if onRampReader not set, return nil error and 0 values
+	require.EqualValues(t, 0, destDataAvailabilityOverheadGas)
+	require.EqualValues(t, 0, destGasPerDataAvailabilityByte)
+	require.EqualValues(t, 0, destDataAvailabilityMultiplierBps)
 	svc.SetOnRampReader(onRampReader)
 
 	onRampReader.On("GetDynamicConfig", ctx).
@@ -35,7 +38,7 @@ func TestFeeEstimatorConfigService(t *testing.T) {
 			DestDataAvailabilityMultiplierBps: uint16(expectedDestDataAvailabilityMultiplierBps),
 		}, nil).Once()
 
-	destDataAvailabilityOverheadGas, destGasPerDataAvailabilityByte, destDataAvailabilityMultiplierBps, err := svc.GetDataAvailabilityConfig(ctx)
+	destDataAvailabilityOverheadGas, destGasPerDataAvailabilityByte, destDataAvailabilityMultiplierBps, err = svc.GetDataAvailabilityConfig(ctx)
 	require.NoError(t, err)
 	require.Equal(t, expectedDestDataAvailabilityOverheadGas, destDataAvailabilityOverheadGas)
 	require.Equal(t, expectedDestGasPerDataAvailabilityByte, destGasPerDataAvailabilityByte)