"del <varname>" in the console is broken

The variable is not removed from the varlist and thus the editor tries to display it on update which evidently fails. Then redefining the variable adds it a second time in the varlist leading to all kinds of "interesting" problems 😭. Very annoying.

Well, it was not as important as I thought, as there was a problem only for "undisplayable" variables, which should be very rare for users. I fixed it anyway.