FrameComponent: check this.iframe is not null before accessing it
FrameComponent: check this.iframe is not null before accessing it

The function renderFrameContents calls itself recursively, in a setTimeout.
React may unmount the component during one of those timeouts which will reset
'this.iframe' to null.

interactivethings/catalog,interactivethings/catalog,interactivethings/catalog,interactivethings/catalog