Fix rendering 0
Fix rendering 0

When a component renders a numerical `0`, the `_currentElement` property
is set to numerical `0`. The check for a "raw" element was inside a
truthy check for `_currentElement`, which in the case of `0` is
obviously false. In the devtools, a rendered `{0}` shows up as `</>`.

aarondancer/react-devtools,aolesky/react-devtools,aarondancer/react-devtools,keyanzhang/react-devtools,jhen0409/react-devtools,aolesky/react-devtools,jhen0409/react-devtools,aarondancer/react-devtools,aolesky/react-devtools,jhen0409/react-devtools,keyanzhang/react-devtools