Fix Rails/FilePath cop error with rescued Rails.root

```console
echo '"#{Rails.root rescue "."}/config"' | rubocop --stdin bug.rb -d

An error occurred while Rails/FilePath cop was inspecting bug.rb:1:0.
undefined method `method?' for an instance of RuboCop::AST::RescueNode
lib/rubocop/cop/rails/file_path.rb:156:in `autocorrect_slash_after_rails_root_in_dstr'
lib/rubocop/cop/rails/file_path.rb:81:in `block in check_for_slash_after_rails_root_in_dstr'
```

Author: viralpraxis

changelog/fix_rails_file_path_cop_error_with_rescued_rails_root.md

@@ -0,0 +1 @@
+* [#1392](https://github.com/rubocop/rubocop-rails/pull/1392): Fix `Rails/FilePath` cop error with rescued `Rails.root`. ([@viralpraxis][])

lib/rubocop/cop/rails/file_path.rb

@@ -76,6 +76,7 @@ def check_for_slash_after_rails_root_in_dstr(node)
           rails_root_index = find_rails_root_index(node)
           slash_node = node.children[rails_root_index + 1]
           return unless slash_node&.str_type? && slash_node.source.start_with?(File::SEPARATOR)
+          return if node.children[rails_root_index].each_descendant(:rescue).any?
 
           register_offense(node, require_to_s: false) do |corrector|
             autocorrect_slash_after_rails_root_in_dstr(corrector, node, rails_root_index)

spec/rubocop/cop/rails/file_path_spec.rb

@@ -406,5 +406,13 @@
         RUBY
       end
     end
+
+    context 'when rescued concat Rails.root' do
+      it 'does not register an offense' do
+        expect_no_offenses(<<~'RUBY')
+          "#{Rails.root rescue '.'}/config"
+        RUBY
+      end
+    end
   end
 end