fix review comments

Signed-off-by: jyjiangkai <[email protected]>

Author: hwjiangkai

client/examples/eventbus/append/main.go

@@ -41,7 +41,7 @@ func main() {
 	if err != nil {
 		panic("invalid id")
 	}
-	bus, err := c.Eventbus(ctx, api.WithName("quick-start"), api.WithID(eventbusID.Uint64()))
+	bus, err := c.Eventbus(ctx, api.WithID(eventbusID.Uint64()))
 	if err != nil {
 		panic(err.Error())
 	}

client/pkg/eventbus/eventbus.go

@@ -512,6 +512,9 @@ func (w *busWriter) pickWritableLog(ctx context.Context, opts *api.WriteOptions)
 	if err != nil {
 		return nil, err
 	}
+	if lw == nil {
+		return nil, errors.ErrResourceCanNotOp.WithMessage("can not pick writable log")
+	}
 
 	return lw.Writer(), nil
 }
@@ -588,6 +591,9 @@ func (r *busReader) pickReadableLog(ctx context.Context, opts *api.ReadOptions)
 	if err != nil {
 		return nil, err
 	}
+	if lr == nil {
+		return nil, errors.ErrResourceCanNotOp.WithMessage("can not pick readable log")
+	}
 
 	return lr.Reader(eventlog.ReaderConfig{PollingTimeout: opts.PollingTimeout}), nil
 }