...ex/texmf-context/scripts/context/lua/mtx-context.lua:563: attempt to
index local 'ctxdata' (a nil value)

So ctxdata is not there ('a nil value')... if you look at line 563, you see
(this line is not indented like the others):

   563 ctxdata.flags.inputfile = filename -- is this right

ah, i was unaware of that bug being in the formal beta

just comment that line

(ctxdata is only there when there is a ctx file and i happen to have them around -)