Make DOMSelection.setSelection() more robust.
Make DOMSelection.setSelection() more robust.

podviaznikov/substance,jacwright/substance,abhaga/substance,andene/substance,TypesetIO/substance,TypesetIO/substance,michael/substance-1,andene/substance,substance/substance,stencila/substance,podviaznikov/substance,abhaga/substance,jacwright/substance,michael/substance-1,substance/substance