Block Editor: link marks with no target render target="null" in Story Block VTL, causing every "same-window" link to open a new tab

Problem Statement

Problem Statement

When a link has no explicit target (the normal case for any link meant to open in the
same window), $mark.attrs.target is null. $esc.html(null) renders the literal string
"null" rather than an empty string, so the output is:

<a href="/some/page" target="null" ...>Some Link

Per the HTML living standard, a target value that isn't one of the reserved keywords
(_blank, _self, _parent, _top) is treated as the name of a browsing context. Since no
browsing context named "null" exists yet, the browser creates a new one — i.e. it opens a
new tab/window — exactly as if target="_blank" had been set. Every same-window link
authored via the Block Editor is affected, on every dotCMS site, whenever the link's target
was never explicitly set.

renderMarks is used by #macro(renderContentBlock) for every text-bearing node (paragraph,
heading, list item, table cell, blockquote), so this hits any Block Editor field rendered via
the traditional (VTL) delivery path.

#macro(renderMarks) in VM_global_library.vm renders the target attribute on every
link mark unconditionally, with no null guard — unlike title, aria-label, and rel
right below it, which are all correctly gated behind #if(...):

https://github.com/dotCMS/core/blob/main/dotCMS/src/main/webapp/WEB-INF/velocity/VM_global_library.vm#L36-L40

*#<a href="${esc.html($mark.attrs.href)}" target="${esc.html($mark.attrs.target)}"#*
*##if($mark.attrs.title) title="${esc.html($mark.attrs.title)}"#end#*
*##if($mark.attrs.get("aria-label")) aria-label="${esc.html($mark.attrs.get("aria-label"))}"#end#*
*##if($mark.attrs.rel) rel="${esc.html($mark.attrs.rel)}"#end#*
*#>#*

### Steps to Reproduce

1. In any Block Editor field, add a text link and leave "Target" unset (the default — do not
2. choose "New window").
3. Publish the page.
4. View the published page and inspect the rendered <a> for that link — note
5. target="null".
6. Click the link — it opens in a new tab, even though no one selected "open in new window."


https://drive.google.com/file/d/1_DPxjfkldqpVj-CZeIffYatpX85DyZL_/view?usp=drive_link

### Acceptance Criteria

Expected: a link with no explicit target renders with no target attribute at all
(or an equivalent same-window value), and opens in the same tab.

Actual: the link renders target="null" and opens in a new tab/window.

### dotCMS Version

26.09.14-01
26.09.17-02

### Severity

Low - Minor issue or cosmetic

### Links

https://dotcms.freshdesk.com/a/tickets/39485

Start in dotCMS/src/main/webapp/WEB-INF/velocity/VM_global_library.vm at #macro(renderMarks), where the link mark target is rendered. Reproduce a Block Editor link with no target through the VTL delivery path and verify that the finished output omits target when it is null and opens in the same tab.