Guard against null content in preparse callback

[sheldonkotyk]

Problem

When Statamic passes null to the preparse callback — for example, when a tag like {{ seo_pro:meta }} returns no value on a 404 page — the AntlersCompiler::compile() method throws a TypeError due to its string type hint:

Stillat\AntlersComponents\AntlersCompiler::compile(): Argument #1 ($content) must be of type string, null given

Fix

Added a guard in the ServiceProvider preparse callback to return non-string values unchanged, allowing the runtime to handle them as it normally would.

Test plan

• Verify pages with tags that can return null (e.g. on 404 pages) no longer throw a TypeError
• Verify normal component compilation still works as expected

🤖 Generated with Claude Code

[JohnathonKoster]

Before you get too far, I'd like to see the dependency updates split off into their own PR to keep the descriptions accurate to the changeset.

Thanks!