Copy page tree - Insert "null" character in prefix and suffix

Versions tested

Confluence 6.6.3 and 6.12.1
ScriptRunner 5.4.9 (The newest version 5.4.36 wasn't tested because there is a bug in Copy Page Tree (SRCONF-542))

Issue

When copy page tree to other space without fill "prefix" and "suffix" fields, the new pages will contain the "null" character in the Title.

Steps to Reproduce

1. Create a page, add a title then create another page with a title in its hierarchy.
2. Create an empty space
3. Clicking in Space tools and then Advanced Space Functionality
4. Select Copy Page Tree Built-in Script
5. Choose the page created in step 1 in the Source page field
6. Choose the new empty space created in step 2 in the Target page field
7. Leave Title Prefix and Suffix empty
8. Clicking on the Run Button

Expected Result

Copy the pages without the "null" character in the title if it has hadn't filled.

In this example, the prefix and suffix are filled.

You can see the result of the copy.

Actual Resul

The pages were created with "null" character in the title prefix and suffix when these fields aren't filled.