[Fizz] Ignore error if content node is gone (facebook#33068)

We normally expect the segment to exist whatever the client does while
streaming. However, when hydration errors at the root of the shell for a
whole document render, then we clear nodes from body which can include
our segments. We don't need them anymore because we switched to client
rendering.

It triggers an error accessing parent node which can safely be ignored.
This just helps avoid confusion in this scenario.

This also covers up the error in facebook#33067. Which doesn't actually cause
any visible problems other than error logging. However, ideally we
wouldn't emit completeBoundary instructions if the boundary is inside a
cancelled fallback.

Author: sebmarkbage

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

@@ -49,6 +49,12 @@ export function clientRenderBoundary(
 
 export function completeBoundary(suspenseBoundaryID, contentID, errorDigest) {
   const contentNode = document.getElementById(contentID);
+  if (!contentNode) {
+    // 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.
+    return;
+  }
   // 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.
   contentNode.parentNode.removeChild(contentNode);