avoid manipulation of text nodes on first repaint

[#56959632]

Error only occurred on Firefox.

An NS_ERROR_FAILURE: Failure related -txtSelection.node().getBBox().width /2) is happening when the charge symbols are rendered. If charge symbols are disabled, the model will load fine.

fyi:
First bad commit produced by git bisect:

commit 4a9cafca7241af04264be5afb778b9af97277c6f
Author: Stephen Bannasch <stephen.bannasch@gmail.com>
Date: Wed Sep 4 12:07:25 2013 -0400

repaint MD2D render when initialized

Otherwise the model calls into the renderer
before variables like objects are setup.
webgl checkbox: pass proxy interactiveController

[#57020306]

The Energy2D model adds a model dialog displayed by
clicking in the lighting bolt icon in the upper
left of the model.

Inside the dialog is a checkbox for enabling or disabling WebGL.

With the recent re-factoring of the way Interactive components are initialized the creation of this CheckboxController inside WebGL status dialog fails.

TODO: still need to find a way to call the modelLoaded
callback in this checkBox controller when the Interactive
is reset.
webgl checkbox works w/subsequent modelLoaded callbacks

[#57020306]

The energy2d model the webgl checkbox is wired to is
now updated correctly after a subsequent modelLoaded
callback.

TODO: what isn't preserved anymore is the actual selection
of whether webgl is enabled after an interactive reloa()
event