RBS raises NoMethodError when a class inherits a module mistakenly

[pocke]

RBS raises an error when a class inherits a module mistakenly.

# test.rbs
module M
end

class C < M
end

$ rbs -I. validate --silent
/path/to/lib/ruby/gems/3.2.0+1/gems/rbs-2.7.0/lib/rbs/definition_builder.rb:393:in `block (2 levels) in build_singleton': undefined method `defs' for nil:NilClass (NoMethodError)

              if new_method.defs.all? {|d| d.defined_in == BuiltinNames::Class.name }
                           ^^^^^
	from <internal:kernel>:90:in `tap'
	from /path/to/lib/ruby/gems/3.2.0+1/gems/rbs-2.7.0/lib/rbs/definition_builder.rb:385:in `block in build_singleton'
	from /path/to/lib/ruby/gems/3.2.0+1/gems/rbs-2.7.0/lib/rbs/definition_builder.rb:860:in `try_cache'
	from /path/to/lib/ruby/gems/3.2.0+1/gems/rbs-2.7.0/lib/rbs/definition_builder.rb:376:in `build_singleton'
	from /path/to/lib/ruby/gems/3.2.0+1/gems/rbs-2.7.0/lib/rbs/cli.rb:443:in `block in run_validate'
	from /path/to/lib/ruby/gems/3.2.0+1/gems/rbs-2.7.0/lib/rbs/cli.rb:438:in `each'
	from /path/to/lib/ruby/gems/3.2.0+1/gems/rbs-2.7.0/lib/rbs/cli.rb:438:in `run_validate'
	from /path/to/lib/ruby/gems/3.2.0+1/gems/rbs-2.7.0/lib/rbs/cli.rb:130:in `run'
	from /path/to/lib/ruby/gems/3.2.0+1/gems/rbs-2.7.0/exe/rbs:7:in `<top (required)>'
	from /path/to/bin/rbs:25:in `load'
	from /path/to/bin/rbs:25:in `<main>'

The test.rbs is actually invalid, but rbs validate should handle this problem instead of NoMethodError. The current behavior confuses RBS beginners.