Simplify SimpleWheelCache.get in case package_name is falsy
Simplify SimpleWheelCache.get in case package_name is falsy

pradyunsg/pip,pradyunsg/pip,pypa/pip,xavfernandez/pip,xavfernandez/pip,pypa/pip,pfmoore/pip,pfmoore/pip,xavfernandez/pip,sbidoul/pip,sbidoul/pip