p2p: limit rate of dialing new peers (#6485)

light/provider/http/http.go

@@ -2,6 +2,7 @@ package http
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"math/rand"
 	"net/url"
@@ -122,6 +123,12 @@ func (p *http) LightBlock(ctx context.Context, height int64) (*types.LightBlock,
 		}
 	}
 
+	if sh.Header == nil {
+		return nil, provider.ErrBadLightBlock{
+			Reason: errors.New("header is nil unexpectedly"),
+		}
+	}
+
 	vs, err := p.validatorSet(ctx, &sh.Height)
 	if err != nil {
 		return nil, err