Cast wp_count_attachments() before iterating it to avoid a notice when items exist without a mime type.

props bobbingwide.
fixes #27802.

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Add missing string translation in widgets.

see #27453, #27112.

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Theme Installer: Fixes for browsers without pushState.

props gcorne.
see #27055.

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TinyMCE: fix icons in IE7, fixes #27829
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Widgets: Remove create_function() from the customizer class.

props westonruter.
fixes #27805.

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