Exception when using irb:rdbg where objectto_s might return nil

[adam12]

The to_s method returning nil is obviously an issue, but we should guard against that anyways.

# test.rb
class SomeObject
  def to_s
    nil
  end

  def do_something
    debugger
  end
end

SomeObject.new.do_something

$ rdbg -e 'config set irb_console 1 ;; c' -c ruby test.rb

/Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/irb-1.15.2/lib/irb.rb:601:in 'IRB::Irb#truncate_prompt_main': undefined method 'tr' for nil (NoMethodError)

      str = str.tr(CONTROL_CHARACTERS_PATTERN, ' ')
               ^^^
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/irb-1.15.2/lib/irb.rb:616:in 'block in IRB::Irb#format_prompt'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/irb-1.15.2/lib/irb.rb:610:in 'String#gsub'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/irb-1.15.2/lib/irb.rb:610:in 'IRB::Irb#format_prompt'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/irb-1.15.2/lib/irb.rb:585:in 'IRB::Irb#generate_prompt'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/irb-1.15.2/lib/irb.rb:242:in 'IRB::Irb#readmultiline'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/irb-1.15.2/lib/irb.rb:270:in 'block in IRB::Irb#each_top_level_statement'
        from <internal:kernel>:168:in 'Kernel#loop'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/irb-1.15.2/lib/irb.rb:269:in 'IRB::Irb#each_top_level_statement'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/irb-1.15.2/lib/irb.rb:192:in 'IRB::Irb#eval_input'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/irb-1.15.2/lib/irb.rb:130:in 'block in IRB::Irb#debug_readline'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/irb-1.15.2/lib/irb.rb:123:in 'Kernel#catch'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/irb-1.15.2/lib/irb.rb:123:in 'IRB::Irb#debug_readline'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/irb-1.15.2/lib/irb/debug/ui.rb:57:in 'block in IRB::Debug::UI#readline'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/irb-1.15.2/lib/irb/debug/ui.rb:76:in 'block in IRB::Debug::UI#setup_interrupt'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:1989:in 'DEBUGGER__::Session#intercept_trap_sigint'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/irb-1.15.2/lib/irb/debug/ui.rb:69:in 'IRB::Debug::UI#setup_interrupt'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/irb-1.15.2/lib/irb/debug/ui.rb:55:in 'IRB::Debug::UI#readline'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:445:in 'DEBUGGER__::Session#wait_command'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:405:in 'block in DEBUGGER__::Session#wait_command_loop'
        from <internal:kernel>:168:in 'Kernel#loop'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:404:in 'DEBUGGER__::Session#wait_command_loop'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:330:in 'DEBUGGER__::Session#process_event'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:255:in 'DEBUGGER__::Session#session_server_main'
        from /Users/adam/.local/share/mise/installs/ruby/3.4.2/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:207:in 'block in DEBUGGER__::Session#activate'