[NTG-context] missing underbrace using palatino with latest beta (2013.12.26)

A minimal example: ----------- cut --------------- \setupbodyfont[palatino,12pt] \starttext \startformula \underbrace{x}_{1} \stopformula \stoptext ----------- cut --------------- It works fine with 2013.05.28 00:36 MKIV current. With 2013.12.26 12:50 MKIV beta, the underbrace disappears. With a bigger target (e.g. "xyz" instead of "x") or with the default font, the underbrace returns. -- -Sanjoy