TYPO3 Core

because of type hinting an fatal error can occur in EXT:lang/lang.php

problem is inside t3lib_div::readLLfile which can give back either a filled array, an empty array or FALSE if there was an error.
therefore the line
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t3lib_div::array_merge_recursive_overrule((array)$LOCAL_LANG, $llang);
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produces a crash because $llang is boolean and not an array.

solution: check if it is an array

(issue imported from #M16825)