Bug 1826167 - Fix Drag Drop Move Messages To Folders from Vertical View, card style message list. r=aleca

Depends on D175747

Differential Revision: https://phabricator.services.mozilla.com/D175825

--HG--
extra : rebase_source : 970a7a437240d769258047380a59eb529874619e

mail/base/content/about3Pane.js

@@ -2920,8 +2920,11 @@ var threadPane = {
     }
   },
 
+  /**
+   * Handle threadPane drag events.
+   */
   _onDragStart(event) {
-    let row = event.target.closest(`tr[is="thread-row"]`);
+    let row = event.target.closest(`tr[is^="thread-"]`);
     if (!row) {
       event.preventDefault();
       return;