add virtual destructor to SrsRefer

@@ -27,6 +27,14 @@ CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #include <srs_kernel_log.hpp>
 #include <srs_app_config.hpp>
 
+SrsRefer::SrsRefer()
+{
+}
+
+SrsRefer::~SrsRefer()
+{
+}
+
 int SrsRefer::check(std::string page_url, SrsConfDirective* refer)
 {
     int ret = ERROR_SUCCESS;

@@ -36,6 +36,9 @@ class SrsConfDirective;
 class SrsRefer
 {
 public:
+    SrsRefer();
+    virtual ~SrsRefer();
+public:
     /**
     * to check the refer.
     * @param page_url the client page url.