Prevent MultipleExceptionError#add from allowing self to be added to the list of all_exceptions

lib/rspec/core/formatters/exception_presenter.rb

@@ -408,6 +408,8 @@ def add(exception)
           # ignore it.
           return if Pending::PendingExampleFixedError === exception
 
+          return if exception == self
+
           all_exceptions << exception
 
           if exception.class.name =~ /RSpec/

spec/rspec/core/formatters/exception_presenter_spec.rb

@@ -695,6 +695,12 @@ def new_multiple_exception_error
       end
     end
 
+    it "does not let you add itself to the list of all_exceptions" do
+      m = MultipleExceptionError.new
+      m.add(m)
+      expect(m.all_exceptions).to_not include(m)
+    end
+
     it 'supports the same interface as `RSpec::Expectations::MultipleExpectationsNotMetError`' do
       skip "Skipping to allow an rspec-expectations PR to add a new method and remain green" if ENV['NEW_MUTLI_EXCEPTION_METHOD']