This PR was merged into the 2.3.x-dev branch.

Discussion
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Check for HttpKernelRuntime before using it in Twig runtimes

Fixes #1448.

This fixes an incompatibility with Symfony Twig bridge prior to 3.2.

The HttpKernelRuntime was introduced in https://github.com/silexphp/Silex/commit/72d7746ec216da230221c19aa6e3092b55596070.
It included checks whether the class exists, but not in the Twig runtimes list.

Commits
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18ab3f6e Check for HttpKernelRuntime before using it in Twig runtimes