TYPO3 Core

1. click "File => Filelist" in the main menu to open the fileadmin of typo3
2. create a folder in fileadmin called "6.4."
3. click on the created folder in fileadmin

=> If you click on this folder you dont get any list on the right side of backend.
=> If you use this folder in T3 you dont have access to it
=> If you want delete the folder you cant delete it, getting a error message calling "Target was not a directory!"

Favoured behavior:
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If anybody create a folder with dots in it, Typo3 should check the name of the folder an give a error-message or something else that a foldername with dots are not allowed

(issue imported from #M8044)