Silence failures to trigger notifications when not available

[astorije]

Fixes #731.

Recent Chrome versions are dropping out new Notification in favor of ServiceWorkerRegistration.showNotification.
This makes sure nothing bad happens until we have proper support for Service Workers.

See:

• https://stackoverflow.com/questions/29774836/failed-to-construct-notification-illegal-constructor
• https://stackoverflow.com/questions/31512504/html5-notification-not-working-in-mobile-chrome

[xPaw]

I would add the same thing in settings, so if notifications can't be created, the option is disabled. Also the sounds can't be played on mobile without user interaction which also throws.

[astorije]

Also the sounds can't be played on mobile without user interaction which also throws.

Added a try/catch for this too.

I would add the same thing in settings, so if notifications can't be created, the option is disabled.

This can only be detected when calling Notification.new so it can't be done in the settings. I'd need to fiddle with the options, localStorage, checkboxes and others to make something nice. For this I would also need to move around things to make sure they are declared in order and in the proper scope.

I'm not comfortable doing so as I'm pretty sure I'll break something at first try, and I don't have much time to give at the moment so I won't be able to do it myself.
I'd say let's fix the bugs reported in #731 for now and UX of that state can be improved later on. What do you think?