When HTML parser fails Modeler HTML tree displays nothing

When the HTML parser fails (for whatever reason) then
the HTML tree tab displays absolutely nothing, and the
structure tab folders have no content. This is
unfortunate because the parsing up to the point of
failure may have been successful and the specifying
DOM identifiers (prior to the parser failure) in the LOAD
RESPONSE_INFO do work if their format can be worked
out without the aid of the GUI.

Causing the HTML parser to fail is usually down to bad
HTML so a workaround is to fix the HTML you are
parsing but sometimes this is not possible. The HTML
parser can be made to fail by something as simple as
missing the closing greater than off the close HTML tag
but this problem report is not about HTML parser
stability.