ZWNJ/ZWJ being shown in Pango HEAD ?

[Sayamindu Dasgupta <sayamindu clai net>]

Hello,
For some reasons, Pango HEAD is showing the glyphs for ZWNJ and ZWJ (I
don't think they are supposed to be displayed).
This does not occur normally (when you insert a standalone ZWNJ), but it
shows up when I write a sequence such as U+0995 U+09CD ZWNJ (ক্‌).
Can anyone explain what is happening here ?
-thanks-
Sayamindu