error/exit and client "lockup" due to bad search string (leading @)

Woo, I got my dev instance running!

I tried to search for my masto account by typing this in the search bar:

@sixohsix@icosahedron.website

This appeared in the logs:

[error] #PID<0.698.0> running Pleroma.Web.Endpoint terminated
Server: xxx:4000 (http)
Request: GET /api/externalprofile/show.json?profileurl=@sixohsix@icosahedron.website
** (exit) :badarg

And the search bar spinner never stopped spinning. I later realized that I had to drop the leading @.

Would be nice to detect and drop the leading @ automatically rather than failing.