fix(gatsby-source-drupal): validate webhook bodies & updated node data (#33079)

* fix(gatsby-source-drupal): validate webhook bodies & updated node data

Fix some errors we've seen on Drupal sites from updates coming. Ideally
we iron out too whatever is triggering malformed/missing updates from coming in.

This will at least not break builds + give us some more info to track down
the deeper issue.

* Clarify warning

Author: KyleAMathews

packages/gatsby-source-drupal/src/gatsby-node.js

@@ -146,6 +146,20 @@ exports.sourceNodes = async (
         changesActivity.end()
         return
       }
+
+      if (!action || !data) {
+        reporter.warn(
+          `The webhook body was malformed
+
+${JSON.stringify(webhookBody, null, 4)}
+
+          `
+        )
+
+        changesActivity.end()
+        return
+      }
+
       if (action === `delete`) {
         let nodesToDelete = data
         if (!Array.isArray(data)) {

packages/gatsby-source-drupal/src/utils.js

@@ -196,6 +196,17 @@ const handleWebhookUpdate = async (
   },
   pluginOptions = {}
 ) => {
+  if (!nodeToUpdate || !nodeToUpdate.attributes) {
+    reporter.warn(
+      `The updated node was empty or is missing the required attributes field. The fact you're seeing this warning means there's probably a bug in how we're creating and processing updates from Drupal.
+
+${JSON.stringify(nodeToUpdate, null, 4)}
+      `
+    )
+
+    return
+  }
+
   const { createNode } = actions
 
   const newNode = nodeFromData(