module.suspend not called if module does not have dom content

[sdetweil]

Please only submit reproducible issues.

If you're not sure if it's a real bug or if it's just you, please open a topic on the forum: https://forum.magicmirror.builders/category/15/bug-hunt
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When submitting a new issue, please supply the following information:

Platform: Ubuntu Mate on ODROID xu4

Node Version: v6.14.2

MagicMirror Version: 2.3.1

Description: my modules, which have no dom content (and no position specified in config) do not receive the suspend notification.

Steps to Reproduce: create the default module as defined in the doc, but only supply the module name in config.js
at this point issue a module.hide() against this module, but its suspend method will not be called.

Expected Results: module suspend() function should be called

Actual Results: suspend not called (resume is)

Configuration: ```
{
module: "ImageScheduler",
},
{
module: "ImageService",
},

**Additional Notes**: Provide any other relevant notes not previously mentioned. This is optional.

this is due to the test for dom content in js/main.js/hideModule()

var moduleWrapper = document.getElementById(module.identifier);
    if (moduleWrapper !== null) {

there should be an else, to invoke the (post fade timeout)callback setup in js/module.js/hide()

}
else
     if (typeof callback === "function") { callback(); }

[MichMich]

Thanks. Feel free to send a PR.

[sdetweil]

pr merged july 2018,
#1309