InteractiveUtils: In `edit(m::Module)`, throw a more informative error when `pathof(m)` is nothing (#61303)
🤖 Discovered via automated Codex audit.
Before this PR, `edit(m::Module)` will throw a relatively unhelpful
error if `pathof(m)` is nothing:
```julia
julia> module MyModule end
julia> InteractiveUtils.edit(MyModule)
ERROR: object is not callable
Stacktrace:
```
After this PR, it throws a more useful error.
🤖 Co-authored-by: Codex
Co-authored-by: Codex <codex@openai.com>