[BUGFIX] Don't render double slashes in file URLs

[kitzberger]

Without a frontendApiProxy in the site config, URLs to local files contain two slashes like www.mysite.org//fileadmin/my-image.jpg

[coveralls]

Pull Request Test Coverage Report for Build 11931576567

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 72.782%

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Totals
Change from base Build 11668288700:	0.0%
Covered Lines:	1083
Relevant Lines:	1488

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💛 - Coveralls