Fix #473 - crash if bearer token is blank

lib/bearerstrategy.js

@@ -526,7 +526,7 @@ Strategy.prototype.authenticate = function authenticateStrategy(req, options) {
                 log.info(`In Strategy.prototype.authenticate: received access_token from request header: ${token}`);
             }              
             else
-              self.failWithLog('In Strategy.prototype.authenticate: missing access_token in the header');
+              return self.failWithLog('In Strategy.prototype.authenticate: missing access_token in the header');
         }
       }