fix(gatsby): Prevent errors if Head has root text node (gatsbyjs#36402)

* Don't break when Head has root text node(s)

* test that we dont break on root text nodes

Author: marvinjude

e2e-tests/development-runtime/src/pages/head-function-export/basic.js

@@ -60,6 +60,7 @@ export function Head() {
       <script type="text/javascript">
         {`window.__SOME_GLOBAL_TO_CHECK_CALL_COUNT__ = (window.__SOME_GLOBAL_TO_CHECK_CALL_COUNT__ || 0 ) + 1`}
       </script>
+      Adding-this-text-here-should-not-break-things
     </>
   )
 }

e2e-tests/production-runtime/src/pages/head-function-export/basic.js

@@ -41,6 +41,7 @@ export function Head() {
       <script type="text/javascript">
         {`window.__SOME_GLOBAL_TO_CHECK_CALL_COUNT__ = (window.__SOME_GLOBAL_TO_CHECK_CALL_COUNT__ || 0 ) + 1`}
       </script>
+      Adding-this-text-here-should-not-break-things
     </>
   )
 }

packages/gatsby/cache-dir/head/head-export-handler-for-browser.js

@@ -28,7 +28,7 @@ const onHeadRendered = () => {
   const seenIds = new Map()
   for (const node of hiddenRoot.childNodes) {
     const nodeName = node.nodeName.toLowerCase()
-    const id = node.attributes.id?.value
+    const id = node.attributes?.id?.value
 
     if (!VALID_NODE_NAMES.includes(nodeName)) {
       warnForInvalidTags(nodeName)

packages/gatsby/cache-dir/head/head-export-handler-for-ssr.js

@@ -57,7 +57,7 @@ export function headHandlerForSSR({
     const seenIds = new Map()
     for (const node of headNodes) {
       const { rawTagName } = node
-      const id = node.attributes.id
+      const id = node.attributes?.id
 
       if (!VALID_NODE_NAMES.includes(rawTagName)) {
         warnForInvalidTags(rawTagName)