Only create a new draft row if duplicating a draft to another draft

CHANGELOG.md

@@ -1,5 +1,8 @@
 # Release Notes for Craft CMS 3.x
 
+## Unreleased
+- Fixed a bug where extra rows could be created in the `drafts` table.
+
 ## 3.6.4 - 2021-02-05
 
 ### Added

src/services/Elements.php

@@ -987,8 +987,8 @@ class Elements extends Component
             throw new UnsupportedSiteException($element, $mainClone->siteId, 'Attempting to duplicate an element in an unsupported site.');
         }
 
-        // If this is a draft, create a new draft row
-        if ($mainClone->draftId) {
+        // If we are duplicating a draft as another draft, create a new draft row
+        if ($mainClone->draftId && $mainClone->draftId === $element->draftId) {
             /** @var ElementInterface|DraftBehavior $element */
             $mainClone->draftId = Craft::$app->getDrafts()->insertDraftRow(Craft::t('app', 'First draft'), null, Craft::$app->getUser()->getId());
         }