Call to getTypo3Language() on null

[liayn]

The current 0.4.0 release causes this error.
Introduced with this code: d371740#diff-451798a418ebe68e6f2f909d6e6a4fccc0e8f2aae4694d1c25d1a029ac67010fR54

Testcase:
There is no content on document root, but only within the language prefixes (like https://example.com/de/)
If someone accesses https://example.com/i-am-no-there/ this error occurs (together with a 500 HTTP response of course)