[TYPO3] uninstalling extension after Fatal Error

[Erik Weber]

After mistakenly installing the sr_language_menu before installing the
static info library and tables that it depends, I installed the static info
library before the tables and have ended up with this error:

TYPO3 Fatal Error: Extension key "static_info_tables" was NOT loaded!
(t3lib_extMgm::extRelPath)

But now, when I attempt to go back to the extension manager to install the
static info tables (or delete the library, for that matter) I continue to
get that error.  In fact, my back-end has disappeared alltogether and all I
see is that error.  And I can't seem to access the install tool anymore
either.  How can I remedy this?

-Erik