Callstack (using ?debug=1):

ve.Document.prototype.selectNodes(range=VeRange { from=-1, to=-1, start=-1, more...}, mode="covered")ve.Document.js (line 116)
ve.ce.Document.prototype.getDirectionFromSelection(selection=VeDmLinearSelection { documentModel=VeDmDocument, range=VeRange, toJSON=function(), more...})ve.ce.Document.js (line 272)
ve.ui.WindowAction.prototype.open(name="meta", data=Object { page="advancedSettings"}, action=undefined)ve.ui.W...tion.js (line 55)
ve.ui.Surface.prototype.execute(triggerOrAction="window", method="open")ve.ui.Surface.js (line 367)
ve.ui.Command.prototype.execute(surface=VeUiDesktopSurface { visible=true, $element={...}, updateThemeClassesPending=false, more...})ve.ui.Command.js (line 39)
ve.ui.Tool.prototype.onSelect()ve.ui.Tool.js (line 84)
OO.ui.ToolGroup.prototype.onMouseKeyUp(e=mouseup clientX=1625, clientY=230)oojs-ui.js (line 7625)
OO.ui.PopupToolGroup.prototype.onMouseKeyUp(e=mouseup clientX=1625, clientY=230)oojs-ui.js (line 10826)
OO.ui.ListToolGroup.prototype.onMouseKeyUp(e=mouseup clientX=1625, clientY=230)oojs-ui.js (line 11087)
OO.ui.ToolGroup.prototype.onCapturedMouseKeyUp(e=mouseup clientX=1625, clientY=230)oojs-ui.js (line 7609)

Relevant code (start=-1):

if ( start < 0 || start > doc.getLength() ) {
		throw new Error( 'Invalid start offset: ' + start );
	}

How to retest - turn a page to a redirect page by removing its content and opening the page settings:

1. enter to some page with content
2. empty the page - e.g ctrl+A & backspace
3. Click on page settings
4. page settings doesn't load. exception in console.

Tested with Firefox.