dabbrev-expand gives an error when it can't complete while
lisp-complete-symbol just gives a message.
I can't see any meaning in that Emacs commands gives errors in cases like
this. Is there anyone who can?
Do you see any problem with this?
If you have debug-on-error set to t it gets very disturbing. It is rather
similar to if isearch should raise an error on a search miss.
There is a special variable `debug-ignored-errors' with the list
of error messages to ignore, and as I see it already contains
"^No dynamic expansion for .* found$". So when debug-on-error
is non-nil, `dabbrev-expand' is not disturbing due to this variable.
Do you have a test case where `debug-ignored-errors' gets ignored?