[Fix #7712] Fix an incorrect autocorrect for Style/OrAssignment

Fixes #7712.

This PR fixes an incorrect autocorrect for `Style/OrAssignment`
when using `elsif` branch.

The following is a reproduction procedure.

```ruby
% cat example.rb
foo = if foo
        foo
      elsif
        bar
      else
        'default'
      end
```

It is changed to the code with syntax error as follows.

```console
% bundle exec rubocop -a --only Style/OrAssignment
(snip)

% cat example.rb
foo ||= elsif
          bar
        else
         'default'

% ruby -c example.rb
example.rb:1: syntax error, unexpected `elsif'
foo ||= elsif
```

The or assignment operator replaced when using `elsif` branch is complicated.
The PR will accept the above case without offense.

CHANGELOG.md

@@ -25,6 +25,7 @@
 * [#7688](https://github.com/rubocop-hq/rubocop/issues/7688): Fix a bug in `Style/MethodCallWithArgsParentheses` that made `--auto-gen-config` crash. ([@buehmann][])
 * [#7203](https://github.com/rubocop-hq/rubocop/issues/7203): Fix an infinite loop error for `Style/TernaryParentheses` with `Style/RedundantParentheses` when using `EnforcedStyle: require_parentheses_when_complex`. ([@koic][])
 * [#7708](https://github.com/rubocop-hq/rubocop/issues/7708): Make it possible to use EOL `rubocop:disable` comments on comment lines. ([@jonas054][])
+* [#7712](https://github.com/rubocop-hq/rubocop/issues/7712): Fix an incorrect autocorrect for `Style/OrAssignment` when using `elsif` branch. ([@koic][])
 
 ### Changes
 

lib/rubocop/cop/style/or_assignment.rb

@@ -34,7 +34,7 @@ class OrAssignment < Cop
             (if
               ({lvar ivar cvar gvar} _var)
               ({lvar ivar cvar gvar} _var)
-              _))
+              $_))
         PATTERN
 
         def_node_matcher :unless_assignment?, <<~PATTERN
@@ -51,7 +51,8 @@ def on_if(node)
         end
 
         def on_lvasgn(node)
-          return unless ternary_assignment?(node)
+          return unless (else_branch = ternary_assignment?(node))
+          return if else_branch.if_type?
 
           add_offense(node)
         end

spec/rubocop/cop/style/or_assignment_spec.rb

@@ -321,4 +321,18 @@
       RUBY
     end
   end
+
+  context 'when using `elsif` statement' do
+    it 'does not register an offense' do
+      expect_no_offenses(<<~RUBY)
+        foo = if foo
+                foo
+              elsif
+                bar
+              else
+                'default'
+              end
+      RUBY
+    end
+  end
 end