Firebug incompatible with LJlogin extension

[Agrestis]

Having the LJlogin extension enabled does all sorts of horrible things
to Firebug - even to the extent of getting an irritating alert 'Type
Error: tr.childNodes has no child properties' every time you click the
style tab. Ironic from an extension that claimed to rid us of the
nuisance of alert debugging!

It also causes the following to be printed after every single element
in the Inspector:
function (obj) { return this.indexOf(obj) != -1; }function (obj) {
return this.concat(); }function (obj, i) { this.splice(i, 0, obj);
}function (obj, obj2) { var i = this.indexOf(obj2); if (i == -1) {
this.push(obj); } else { this.splice(i, 0, obj); } }function (i) {
this.splice(i, 1); }function (obj) { var i = this.indexOf(obj); if (i
!= -1) { this.splice(i, 1); } }

And the appearance of errors in the console becomes very erratic -
sometimes they are there, sometimes they aren't.

A fun little problem for someone to work out when they have a spare
afternoon!