Related Question: Why aren't there warnings in the FE as the caches get
initialized in tslib_fe's constructor which is also before a DB conection
exsits?
+ Assumption Ingo Renner: Is a custom error_reporting level causing that?
+
+ There's also an unit test for that check (also deactivated for now
$result = $GLOBALS['TYPO3_DB']->exec_SELECTgetRows(
'id',