Change ValidateSession() to SessionIsActive() which only returns a bool

cmd/calls/images.go

@@ -10,7 +10,7 @@ import (
 
 func ServeImage(c *b.Config, s map[string]*f.Session) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		if _, err := f.ValidateSession(w, r, c, s); err != nil {
+		if !f.SessionIsActive(r, s) {
 			if !tokenIsVerified(w, r, c) {
 				return
 			}