[Fix rubocop#12668] Fix an incorrect autocorrect for `Lint/EmptyCondi…

…tionalBody`

Fixes rubocop#12668.

This PR fixes an incorrect autocorrect for `Lint/EmptyConditionalBody`
when missing `if` body with conditional `else` body.

changelog/fix_an_incorrect_autocorrect_for_lint_empty_conditional_body.md

@@ -0,0 +1 @@
+* [#12668](https://github.com/rubocop/rubocop/issues/12668): Fix an incorrect autocorrect for `Lint/EmptyConditionalBody` when missing `if` body with conditional `else` body. ([@koic][])

lib/rubocop/cop/lint/empty_conditional_body.rb

@@ -104,7 +104,7 @@ def remove_empty_branch(corrector, node)
         def correct_other_branches(corrector, node)
           return unless require_other_branches_correction?(node)
 
-          if node.else_branch&.if_type?
+          if node.else_branch&.if_type? && !node.else_branch.modifier_form?
             # Replace an orphaned `elsif` with `if`
             corrector.replace(node.else_branch.loc.keyword, 'if')
           else

spec/rubocop/cop/lint/empty_conditional_body_spec.rb

@@ -208,6 +208,38 @@ class Foo
     RUBY
   end
 
+  it 'registers an offense for missing `if` body with conditional `else` body' do
+    expect_offense(<<~RUBY)
+      if condition
+      ^^^^^^^^^^^^ Avoid `if` branches without a body.
+      else
+        do_something if x
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      unless condition
+        do_something if x
+      end
+    RUBY
+  end
+
+  it 'registers an offense for missing `unless` body with conditional `else` body' do
+    expect_offense(<<~RUBY)
+      unless condition
+      ^^^^^^^^^^^^^^^^ Avoid `unless` branches without a body.
+      else
+        do_something if x
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      if condition
+        do_something if x
+      end
+    RUBY
+  end
+
   it 'registers an offense for missing `unless` and `else` body' do
     expect_offense(<<~RUBY)
       unless condition