[Fix rubocop#12691] Fix an error for Style/MultilineTernaryOperator

Fixes rubocop#12691.

This PR fixes an error for `Style/MultilineTernaryOperator`
when nesting multiline ternary operators.

lib/rubocop/cop/style/multiline_ternary_operator.rb

@@ -47,7 +47,11 @@ def on_if(node)
           message = enforce_single_line_ternary_operator?(node) ? MSG_SINGLE_LINE : MSG_IF
 
           add_offense(node, message: message) do |corrector|
+            next if part_of_ignored_node?(node)
+
             autocorrect(corrector, node)
+
+            ignore_node(node)
           end
         end
 

spec/rubocop/cop/style/multiline_ternary_operator_spec.rb

@@ -50,6 +50,28 @@
     RUBY
   end
 
+  it 'registers an offense and corrects when nesting multiline ternary operators' do
+    expect_offense(<<~RUBY)
+      cond_a? ? foo :
+      ^^^^^^^^^^^^^^^ Avoid multi-line ternary operators, use `if` or `unless` instead.
+        cond_b? ? bar :
+        ^^^^^^^^^^^^^^^ Avoid multi-line ternary operators, use `if` or `unless` instead.
+          cond_c? ? baz : qux
+    RUBY
+
+    expect_correction(<<~RUBY)
+      if cond_a?
+        foo
+      else
+        if cond_b?
+        bar
+      else
+        cond_c? ? baz : qux
+      end
+      end
+    RUBY
+  end
+
   it 'registers an offense and corrects when everything is on a separate line' do
     expect_offense(<<~RUBY)
       a = cond ?