[luatex] Accessing primitive registers

[Joseph Wright]

Hello all,

Trying to use e.g. tex.dimen for accessing primitives seems to lead to
very odd errors:

  \directlua{print(tex.dimen["pagewidth"])}

    ! LuaTeX error [\directlua]:1: incorrect index value -11 for
    tex.getdimen()
    stack traceback:
	    [C]: in function '__index'

I'm assuming this is a bug?

Joseph