Respect empty_item_single_line config option when formatting empty impls

src/items.rs

@@ -750,7 +750,7 @@ pub fn format_impl(
             result.push_str(&outer_indent_str);
         }
 
-        if result.ends_with('{') {
+        if result.ends_with('{') && !context.config.empty_item_single_line() {
             result.push_str(&sep);
         }
         result.push('}');