fix: guard against undefined attach in setFragmentData

When domRange.cloneContents() returns an empty DocumentFragment (e.g.
because React re-rendered the DOM between selection and copy event),
attach is undefined and setAttribute crashes. Add an early return guard.

Fixes REACT-AND-STIMULUS-1CRK (695 events, 471 users).

Co-Authored-By: Claude Opus 4.6 via Claude Code <noreply@anthropic.com>

Author: mathio

dist/components/editable.d.ts.map

@@ -1050,6 +1050,13 @@ const setFragmentData = (
     }
   })
 
+  // COMPAT: If the cloned contents are empty (e.g. because the DOM was
+  // re-rendered between the selection being set and the copy event firing),
+  // bail out to avoid a crash on setAttribute below.
+  if (!attach) {
+    return
+  }
+
   // COMPAT: If the end node is a void node, we need to move the end of the
   // range from the void node's spacer span, to the end of the void node's
   // content, since the spacer is before void's content in the DOM.