Just check if the parentNode is gone

Author: eps1lon

packages/react-dom-bindings/src/server/fizz-instruction-set/ReactDOMFizzInstructionSetInlineCodeStrings.js

@@ -34,15 +34,15 @@ export function revealCompletedBoundaries(batch) {
   for (let i = 0; i < batch.length; i += 2) {
     const suspenseIdNode = batch[i];
     const contentNode = batch[i + 1];
-    if (contentNode.isConnected) {
+    if (contentNode.parentNode === null) {
+      // If the client has failed hydration we may have already deleted the streaming
+      // segments. The server may also have emitted a complete instruction but cancelled
+      // the segment. Regardless we can ignore this case.
+    } else {
       // We can detach the content now.
       // Completions of boundaries within this contentNode will now find the boundary
       // in its designated place.
       contentNode.parentNode.removeChild(contentNode);
-    } else {
-      // If the client has failed hydration we may have already deleted the streaming
-      // segments. The server may also have emitted a complete instruction but cancelled
-      // the segment. Regardless we can ignore this case.
     }
     // Clear all the existing children. This is complicated because
     // there can be embedded Suspense boundaries in the fallback.