fix: patch PDFIframe to strip trailing whitespace nodes during sign item rendering

static/src/js/sign_image_upload.js

@@ -213,3 +213,29 @@ patch(SignablePDFIframe.prototype, {
         return super.getSignatureValueFromElement(...arguments);
     }
 });
+
+/**
+ * FIX: Odoo Core Bug where trailing whitespace on custom items causes target.lastChild to be a Text Node.
+ * This patch intercepts the insertAdjacentHTML during renderSignItem to strip trailing whitespace nodes immediately,
+ * without modifying Odoo Enterprise source code.
+ */
+patch(PDFIframe.prototype, {
+    renderSignItem(signItemData, target) {
+        if (target && target.insertAdjacentHTML) {
+            const originalInsert = target.insertAdjacentHTML;
+            target.insertAdjacentHTML = function(position, text) {
+                originalInsert.call(this, position, text.trim());
+                // Remove trailing whitespace nodes injected by QWeb
+                while (this.lastChild && this.lastChild.nodeType !== 1) { // 1 == ELEMENT_NODE
+                    this.lastChild.remove();
+                }
+            };
+            try {
+                return super.renderSignItem(...arguments);
+            } finally {
+                target.insertAdjacentHTML = originalInsert;
+            }
+        }
+        return super.renderSignItem(...arguments);
+    }
+});