Thanks for the comments and feedback.
This change is not changing existing behavior. It is adding behavior in the form of a new sub command which amounts to a more succinct way to express something than what currently exists.
So instead of writing things like (which is suggested above)
set a [expr {[dict exists dict_val key] ? [dict get dict_val key] : ""}]
-or-
if { [dict exists dict_val key] && [dict get dict_val key] ne "" } ...
we could write
set a [dict getnull dict_val key]
-or-
if { [dict getnull dict_val key] ne "" } ...
I am considering adding it to my systems and wondered if the community would find value in it and where it made the most sense to place something like this.
-Tony
