Theme Customizer: Javascript errors in Internet Explorer are blocking live previews from displaying

[designsimply]

Steps to reproduce:

1. Install r21383 or later.
2. Go to Appearance → Themes and click Customize.

• Expected: to see customizer panels on the left and a live preview on the right.
• Actual: the live previews are always blank in IE9 and the following Javascript error appears in the console:

SCRIPT5007: Unable to get value of the property ‘detach’: object is null or undefined
customize-controls.js?ver=3.5-alpha-21589, line 194 character 6

[SergeyBiryukov]

To reproduce, select a theme with custom header support (e.g. Twenty Eleven).

"Upload New" tab was removed in [21383], however the uploader is still initialized in that control.

IE doesn't pass the drag-and-drop check in line 187 and fails in line 194:
​http://core.trac.wordpress.org/browser/trunk/wp-admin/js/customize-controls.js?rev=21592#L183

21707.patch​ only initializes the uploader if "Upload New" tab exists.

[azaozz]

Was looking at this too, 21707.patch works well. A bit unsure if we should be looking at the tab name/id to determine if there should be an instance of the uploader, but it works.

[nacin]

[21722] for trunk.

[nacin]

In [21724]:

Remove custom header uploads from the customizer.

For the 3.4 branch. It will return when crop ability is added.

props koopersmith.
see #21355. fixes #21515. fixes #21707.
merges [21379] [21380] [21383] [21385] [21386] [21497] [21722].