fix FilterHandler crash issue

Filter Handler will crash with error assignment to entry in nil map , params from function Tree.Match() maybe nil.

@@ -616,6 +616,9 @@ func (p *ControllerRegistor) ServeHTTP(rw http.ResponseWriter, r *http.Request)
 					}
 					if ok, params := filterR.ValidRouter(urlPath); ok {
 						for k, v := range params {
+							if context.Input.Params == nil {
+								context.Input.Params = make(map[string]string)	
+							}
 							context.Input.Params[k] = v
 						}
 						filterR.filterFunc(context)
@@ -699,9 +702,11 @@ func (p *ControllerRegistor) ServeHTTP(rw http.ResponseWriter, r *http.Request)
 						p[strconv.Itoa(k)] = v
 					}
 				}
+				if p != nil {
 					context.Input.Params = p
 				}
 			}
+		}
 
 	}