fs: ext4: correct error handling

After calling strdup() check the returned pointer.

Avoid a memory leak if the directory is not found.

Reported-by: Michael Nazzareno Trimarchi <michael@amarulasolutions.com>
Fixes: 22fdac381f98 ("fs: ext4: implement opendir, readdir, closedir")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
1 file changed