Fix error in some situations with iframes
Fix error in some situations with iframes

When using popper in an iframe, if the elements are created in the code's global context and added to the iframe, exceptions are thrown because prototypeOf does not accurately assess which nodes are Elements or HTMLElements.

This fixes https://github.com/popperjs/popper-core/issues/1018.
FezVrasta/popper.js,floating-ui/floating-ui,floating-ui/floating-ui,FezVrasta/popper.js,FezVrasta/popper.js,floating-ui/floating-ui,FezVrasta/popper.js