TYPO3 Core

It results in:
TYPO3 Fatal Error: Extension key "" was NOT loaded! (t3lib_extMgm::extRelPath)

New error (RFC 14061) reveals:
#2165053879: TYPO3 Fatal Error: Extension key "" was NOT loaded!

InvalidArgumentException thrown in file
D:\TYPO3\TYPO3 Core Sources SVN\trunk\t3lib\class.t3lib_extmgm.php in line 176.

t3lib_extMgm::extRelPath(NULL)

trunk\typo3\sysext\rtehtmlarea\class.tx_rtehtmlarea_base.php:

00441: $this->addStyleSheet(
00442: 'rtehtmlarea-plugin-' . $pluginId . '-skin',
00443: ($this->is_FE() ? t3lib_extMgm::siteRelPath($key) : t3lib_extMgm::extRelPath($key)) . $pathToSkin
00444: );
00445: }

$key is NULL, should by $this->ID
(issue imported from #M14062)