Bug: redundant (repeated) slash after themes and modules directories

So it produces paths like C:/work/mage2.pro/store/app/code//Magento/Backend/view/adminhtml/templates/menu.phtml

See on redundant (repeated) slash after app/code.

The probjem method is \Magento\Framework\View\Design\Fallback\RulePool::createTemplateFileRule

How to fix it

See the code:

Remove the slashes after $themesDir and $modulesDir variables (at 4 places).