[NTG-context] Very strange bug related to textbackground

[Sanjoy Mahajan]

I don't have a fix, only chiming in that I've seen the same issue.  It
happened when I was learning about backgrounds, so I figured it was my
ignorance and didn't save the test file.  But I'll try to reconstruct
it.

-Sanjoy

`Never underestimate the evil of which men of power are capable.'
         --Bertrand Russell, _War Crimes in Vietnam_, chapter 1.