[Fix #12461] Make Style/StringChars aware of safe navigation operator

Fixes #12461.

This PR makes `Style/StringChars` aware of safe navigation operator.

changelog/fix_make_style_string_chars_aware_of_safe_navigation_operator.md

@@ -0,0 +1 @@
+* [#12461](https://github.com/rubocop/rubocop/issues/12461): Make `Style/StringChars` aware of safe navigation operator. ([@koic][])

lib/rubocop/cop/style/string_chars.rb

@@ -35,6 +35,7 @@ def on_send(node)
             corrector.replace(range, 'chars')
           end
         end
+        alias on_csend on_send
       end
     end
   end

spec/rubocop/cop/style/string_chars_spec.rb

@@ -45,6 +45,17 @@
     RUBY
   end
 
+  it 'registers and corrects an offense when using safe navigation `split(//)` call' do
+    expect_offense(<<~RUBY)
+      string&.split(//)
+              ^^^^^^^^^ Use `chars` instead of `split(//)`.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      string&.chars
+    RUBY
+  end
+
   it 'does not register an offense when using `chars`' do
     expect_no_offenses(<<~RUBY)
       string.chars