Incorrect backpath used when including default and skin stylesheets
CSS paths in typo3/template.php are currently calculated using $GLOBALS['BACK_PATH']. Elsewhere in t3lib_tceforms, $this->backPath is used instead of $GLOBALS['BACK_PATH]. $GLOBALS['BACK_PATH'] may not be available in all contexts, leading to missing styles.
The issue can easily be seen in frontend editing, where the CSS for sprite images is not loaded due to the incorrect path. In this instance $this->backPath is set properly and used elsewhere in t3lib_tceforms but $GLOBALS['BACK_PATH'] is not.
In previous versions of TYPO3, $this->backPath was not set at all in the backend context because all of the views were directly inside /typo3/ and no back path was needed. After moving list view and other modules to extensions, a back path is needed so the first hunk in this patch sets $this->backPath to $GLOBALS['BACK_PATH'] in the normal backend context. While its related to this patch, it could also be a followup to RFCs 15149-15155.
(issue imported from #M15242)