TYPO3 Core

i try to add a own sprite css with

$icons = array(
'extensions-myextension-icon1',
'extensions-myextension-icon2'
);
t3lib_SpriteManager::addIconSprite(
$icons,
t3lib_extMgm::siteRelPath('myextension') . 'myextension_sprite.css'
);

(example from http://blog.tolleiv.de/2010/07/typo3-4-4-sprites-in-your-extension/)

then i got a php Warning
PHP Warning: array_merge() [function.array-merge]: Argument #1 is not an array in /.../t3lib/class.t3lib_spritemanager.php line 211

array_merge try to merge $GLOBALS['TBE_STYLES']['spritemanager']['spriteIconsAvailable'] and $icons but $GLOBALS['TBE_STYLES']['spritemanager']['spriteIconsAvailable'] is no array

testet with current trunk 8664
(issue imported from #M15543)