atskin issue with MultiSelect in normalErrorFocused state.

This PR fixes an issue for the MultiSelect in the `atskin` skin.
When the MultiSelect is in the error state, if it is focused, the following JavaScript error is thrown:
error in aria.widgets.frames.FrameWithIcons, method: _computeIconSize: ICON_NOT_FOUND

The issue comes from an extra colon in the name of the icon.