Sound menu should only display Other vibrations if there is a sensor for vibrations

[Dave Morley]

STEPS:
1. Install the latest iso on a pc
2. Login to the unity8 session
3. Open system settings
4. Open the sound menu

EXPECTED:
I don't expect to see options for other vibrations on a system with no vibrate sensor like a pc

ACTUAL:
Other vibrations is there visible along with Vibrate with message sound and vibrate in silent mode

[Ken VanDine (ken-vandine)]

It might be better to display them but disabled since there would be no effect if you do change them. We'll discuss this.

[Matthew Paul Thomas (mpt)]

The design guidelines I wrote for disabling vs. hiding controls <https://goo.gl/1ZnLyk> (Canonical-only link, sorry):
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In general, you should *disable* a control if it is unusable or irrelevant to the current situation, but there is something the user could reasonably do to make it usable/relevant — for example, changing the value of another control, selecting something, or connecting to the Internet.

You should *hide* a control altogether if it is unusable or irrelevant to the current situation, and there _is not_ anything the user could reasonably do to make it usable/relevant — for example, if the feature can’t work with their hardware, or if it is for editing a message that has already been sent.

What counts as something a user could “reasonably do” is subjective. You might also hide a control if it would normally be disabled, but it is likely to be highly distracting, or if space is at a premium. For example, an image formatting toolbar might appear only when you are editing an image, hiding at other times.
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A PC with no vibration motor falls squarely into the category of “the feature can’t work with their hardware”, so you should hide the control in this case. Specification updated. <https://wiki.ubuntu.com/Sound?action=diff&rev2=178&rev1=177>