解决登录b2b后出现/undefined的情况

src/main/java/com/uas/platform/b2b/controller/SecurityController.java

@@ -146,7 +146,8 @@ public class SecurityController {
 					SystemSession.setUser(user);
 					log(request, user);
 				}
-				return new ModelMap("returnUrl", returnUrl);
+				// returnUrl有时候为null，然后生成URL的时候会出现undefined
+				return new ModelMap("returnUrl", returnUrl==null?"":returnUrl);
 			}
 		}
 		return null;