handle nil body for JSON binding (#1638)

binding/json.go

@@ -6,6 +6,7 @@ package binding
 
 import (
 	"bytes"
+	"fmt"
 	"io"
 	"net/http"
 
@@ -24,6 +25,9 @@ func (jsonBinding) Name() string {
 }
 
 func (jsonBinding) Bind(req *http.Request, obj interface{}) error {
+	if req == nil || req.Body == nil {
+		return fmt.Errorf("invalid request")
+	}
 	return decodeJSON(req.Body, obj)
 }