ido-completing-read-plus not compatible with Sly's "sly-who-calls" function

[ndrvtl]

Hi,

I've found out that I can consistently "crash" the sly-who-calls function in Sly (https://github.com/joaotavora/sly) unless the sly-read-symbol-name is added to the blacklisted functions. The crash closes the connection with the Lisp client with an error.

For the moment it's the only problematic function I've found with Sly.

I'll create a related PR for this issue.