fix: handle potential null properties in SuperConverter

- Updated the SuperConverter class to safely access the 'Properties' element in custom XML, ensuring that the code handles cases where the element may not exist.
- This change improves the robustness of the document conversion process by preventing potential runtime errors.

Author: caio-pizzol

packages/super-editor/src/core/super-converter/SuperConverter.js

@@ -218,7 +218,8 @@ class SuperConverter {
     if (!docx[customLocation]) docx[customLocation] = generateCustomXml();
 
     const customXml = docx[customLocation];
-    const properties = customXml.elements.find((el) => el.name === 'Properties');
+    const properties = customXml.elements?.find((el) => el.name === 'Properties');
+    if (!properties) return null;
     if (!properties.elements) properties.elements = [];
 
     // Check if property already exists