Fix autoload issue with roave/better-reflection SourceLocator Psr0Mapping

[alexander-schranz]

While give roave/backward-compatibility-check a try I stumbled over that it don't like the PSR Mapping of this package.

In InvalidPrefixMapping.php line 15:

  [Roave\BetterReflection\SourceLocator\Type\Composer\Psr\Exception\InvalidPrefixMapping]
  An invalid empty string provided as a PSR mapping prefix


Exception trace:
  at /Users/alexanderschranz/Documents/Projects/sulu-develop.localhost/vendor/sulu/sulu/vendor/roave/better-reflection/src/SourceLocator/Type/Composer/Psr/Exception/InvalidPrefixMapping.php:15
 Roave\BetterReflection\SourceLocator\Type\Composer\Psr\Exception\InvalidPrefixMapping::emptyPrefixGiven() at /Users/alexanderschranz/Documents/Projects/sulu-develop.localhost/vendor/sulu/sulu/vendor/roave/better-reflection/src/SourceLocator/Type/Composer/Psr/Psr0Mapping.php:83

[alexander-schranz]

I'm to unfamiliar with Behat to have a look at the failing CI parts. As the other tests run as expected, I think the issue is unrelated to the autoload changes. /cc @dbu @dantleech

[dbu]

i just did #229 to be sure, and yes, this seems caused by 3rd party effects. will merge this adjustment, thanks!

[dbu]

i tagged it https://github.com/phpcr/phpcr-shell/releases/tag/1.6.2

[alexander-schranz]

@dbu Thx