[BUGFIX] baseUrlWrap can handle url without scheme again

Since #54091 the baseUrlWrap method can't handle urls
without a scheme anymore. Fix this by checking the scheme
exists or not.

Resolves: #76403
Releases: master,7.6
Change-Id: I2a28519ef1fbafd245ececaa4b6cbedc716c0fa5
Reviewed-on: https://review.typo3.org/48583


Reviewed-by: Joerg Boesche <typo3@joergboesche.de>
Tested-by: Joerg Boesche <typo3@joergboesche.de>
Reviewed-by: Susanne Moog <typo3@susannemoog.de>
Tested-by: Susanne Moog <typo3@susannemoog.de>