route: return route on Queries parameter error instead of nil

route.go

@@ -464,16 +464,18 @@ func (r *Route) PathPrefix(tpl string) *Route {
 //
 // - {name:pattern} matches the given regexp pattern.
 func (r *Route) Queries(pairs ...string) *Route {
-	length := len(pairs)
-	if length%2 != 0 {
-		r.err = fmt.Errorf(
-			"mux: number of parameters must be multiple of 2, got %v", pairs)
-		return nil
-	}
-	for i := 0; i < length; i += 2 {
-		if r.err = r.addRegexpMatcher(pairs[i]+"="+pairs[i+1], regexpTypeQuery); r.err != nil {
+	if r.err == nil {
+		length := len(pairs)
+		if length%2 != 0 {
+			r.err = fmt.Errorf(
+				"mux: number of parameters must be multiple of 2, got %v", pairs)
 			return r
 		}
+		for i := 0; i < length; i += 2 {
+			if r.err = r.addRegexpMatcher(pairs[i]+"="+pairs[i+1], regexpTypeQuery); r.err != nil {
+				return r
+			}
+		}
 	}
 
 	return r

route_test.go

@@ -152,3 +152,49 @@ func TestRouteMetadata(t *testing.T) {
 		router.ServeHTTP(rw, req)
 	})
 }
+
+func TestQueriesOddParameters(t *testing.T) {
+	r := NewRouter()
+	route := r.NewRoute().Queries("odd")
+	if route == nil {
+		t.Fatal("Expected route to not be nil")
+	}
+	err := route.GetError()
+	if err == nil {
+		t.Fatal("Expected an error for odd number of query parameters")
+	}
+	expected := "mux: number of parameters must be multiple of 2, got [odd]"
+	if err.Error() != expected {
+		t.Errorf("Expected error %q, got %q", expected, err.Error())
+	}
+
+	// Verify method chaining does not panic
+	chained := r.NewRoute().Queries("odd").Path("/test").Methods("GET")
+	if chained == nil {
+		t.Fatal("Expected chained route to not be nil")
+	}
+	if chained.GetError() == nil {
+		t.Fatal("Expected chained route to retain error")
+	}
+
+	// Verify route does not match
+	req := newRequest("GET", "/test?odd=1")
+	match := new(RouteMatch)
+	if chained.Match(req, match) {
+		t.Error("Expected route with error to not match")
+	}
+}
+
+func TestQueriesExistingError(t *testing.T) {
+	r := NewRouter()
+	route := r.NewRoute().Path("][invalid regexp")
+	initialErr := route.GetError()
+	if initialErr == nil {
+		t.Fatal("Expected path regexp error")
+	}
+
+	route.Queries("k1", "v1")
+	if route.GetError() != initialErr {
+		t.Errorf("Expected initial error to be preserved, got %v", route.GetError())
+	}
+}