Block Supports: Guard against non-string attribute values to avoid fatal errors (Backport for GB #80501)

[im3dabasia]

Trac ticket:

What?

Backport PR of #80494

Guards block supports callbacks against non-string (and other wrong-typed) attribute values so they no longer cause fatalTypeErrors on the front end. (Block support is handled in a this PR.)

Why?

block.json / theme.json types aren't enforced at render time, so wrong-typed values from hand-editing, imports, or AI-generated content reach strict PHP ops (explode, preg_match, str_contains, addcslashes, parse_url, array_column, wp_strip_all_tags, array offsets) and fatal in PHP 8+.

How?

Following the existing idiom guard with is_string() / is_array() / is_scalar() before each strict op and treat a wrong-typed value as absent.

Testing Instructions

Existing tests should pass

Testing Instructions for Keyboard

N/A — no UI changes.

Use of AI Tools

Claude Code

[github-actions]

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