elementary-tweaks depends on ubuntu-overlay-scrollbars gsettings schema

Using Arch Linux too, confirmed this is because of the overlay scrollbar. Using ubuntu-patched gtk reportedly allows elementary-tweaks to launch.

Changed title to be more specific.

There are a couple of these bugs at the moment. They wouldn't be noticed by users of Elementary OS: only users who have installed some /parts/ of the elementary suite will encounter them.

In this case, installing elementary-tweaks but not ubuntu-overlay-scrollbars (ie, non-ubuntu derivative users)

This bug comes from code in src/Settings/GnomeSettings.vala:

http://bazaar.launchpad.net/~versable/elementary-community/elementary-tweaks/view/head:/src/Settings/GnomeSettings.vala

Since elementary-tweaks features a toggle for ubuntu-overlay-scrollbars, but not every distribution ships the package, I can think of three ways to resolve this:

0. Remove the toggle; force users to find another way to (not) customize their scrollbars.
I like having options so this isn't my favourite proposal, but it might be the easiest to implement with the least complications.

1. Add logic to detect if ubuntu-overlay-scrollbars is installed; load elementary-tweaks without the toggle, or with the toggle disabled, if not installed.
I think this is the best idea, but it would require significant changes to the code to implement.
There may be cause for implementing such changes anyway, as similar bugs are likely to occur if users attempt to use elementary-tweaks in the absence of other Elementary OS components that it's designed to customize.

2. Add a dependency on ubuntu-overlay-scrollbars to the packaging; increasing the installation size for elementary-tweak on non-Ubuntu derivative distributions.
Minimalists wouldn't like it and neither would the users who hate ubuntu-overlay-scrollbars (some people really do hate them).
This also sets a precedent to add a dependency for other packages with settings that elementary-tweaks can customize, as they are likely to produce similar bugs when absent. That wouldn't be totally out of order for Elementary OS packages, but would again increase the installation size (exponentially).

I have the same problem using the package elementary-desktop on Ubuntu 14.04 as descried here: http://www.reddit.com/r/elementaryos/comments/283pq0/possible_to_install_pantheon_desktop_in_ubuntu/