Revert "[BUGFIX] Throw Exception if typo3 extension repository is not defined"

This reverts commit c24f31bb6aa426ffaab6861bc44c0e3c440c8b19

Change-Id: Iab42d03d47ae0d8478414bec4d546a91f9d31ffc
Reviewed-on: https://review.typo3.org/19654
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn