classes with a description containing the @global tag will be ignored

in the following example, two classes are declared, the second one extending the first one. The second one uses @global and this make documentation to ignore it. Its inner method appears in the output as a global function.

Expected behavior: there should be a class BaseComponent in the output with a method extend

```js
/**
* blabalbal
*/
class EventEmitter {
/**
* @param {String} eventName
* @param {Function} listener
*/
on(eventName, listener){}
}

/**
* Base abstract class for front-end components. Use method {@link BaseComponent.extend} to build concrete components.
* @class
* @extends EventEmitter
* @hideconstructor
* @global
*/
class BaseComponent extends EventEmitter {
constructor() {
super()
}

/**
* Extends the current component to generate a child one
* @param {{}} componentDefinition Any object with properties/methods that will be used to generate the Component that will be returned
* @return {BaseComponent}
*/
extend(componentDefinition) {
return new BaseComponent();
}
}

```
* What version of documentation.js are you using?: 6.1.0
* How are you running documentation.js (on the CLI, Node.js API, Grunt, other?): node.js