indent level not correctly reset when error happens in html

Nobody has claimed this yet.

sample example. the problem can get a lot worse if the error is nested deep inside some Hypertext, resulting in unreadable `html` output and making debugging hard.
```
i1 : needsPackage"Text"

o1 = Text

o1 : Package

i2 : html DIV "a"

o2 =

i3 : a=new Type of List; html a := x -> 1/0; b=new a;

i6 : new VerticalList from {b}

o6 = {{}}

o6 : VerticalList

i7 : html oo
stdio:3:36:(3):[17]: error: division by zero

i8 : html DIV "a"

o8 =

Start by running the Macaulay2 REPL commands shown in the issue, especially the failing `html oo` evaluation followed by `html DIV "a"`. Trace the HTML rendering and error-handling path to find where indentation state is retained. Done means an error does not affect indentation in subsequent HTML output, including errors nested inside HTML.

Written by the indexing model from the issue text.