Version information:

    ConTeXt  ver: 2016.04.30 18:59 MKIV beta  fmt: 2016.4.30  int:
    english/english
    luajittex, 0.95.0 and luatex, 0.95.0

    running on Windows 10 x64

Error message:

    error:
    ...eXt/tex/texmf-context/tex/context/base/mkiv/font-otj.lua:1205:
    attempt to index local 'i' (a nil value)
    tex error       > tex error on line 7 in file
    C://Users/rik/Desktop/comp_body.tex: ?

Code:

    \setupdirections [bidi=global]
    \definefont [hebrew] [default] [lang=heb,ccmp=yes,script=hebr]
    \definefont [Hebrew] [sileotsr*hebrew sa .9]
    \starttext
      \startparagraph
       Hebrew : {\Hebrew רִ}
      \stopparagraph
    \stoptext

When the first line is removed, or the value of bidi changed to on, no 
error is thrown.

A single-font version of the code, for fonts that have Hebrew glyphs, 
fails with some fonts (libertine shown below), but works with others, 
for example, dejavu sans.

Code:

    \setupdirections [bidi=global]
    \setupbodyfont[libertine]
    \starttext
      \startparagraph
       Hebrew : רִ
      \stopparagraph
    \stoptext

My installation, or is this a bug?

-- 
Rik Kabel