Ignore error if content node is gone

Author: sebmarkbage

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

@@ -51,6 +51,9 @@ export function completeBoundary(suspenseBoundaryID, contentID, errorDigest) {
   const contentNode = document.getElementById(contentID);
   // We'll detach the content node so that regardless of what happens next we don't leave in the tree.
   // This might also help by not causing recalcing each time we move a child from here to the target.
+  if (!contentNode) {
+    return;
+  }
   contentNode.parentNode.removeChild(contentNode);
 
   // Find the fallback's first element.