2a20415140e222bcb09da19d5f36494c26c4d715  Null-check history items in history dumping testing code

Classified as not security-relevant.
Triage note: Internals::getReferencedFilePaths and WebPage::dumpHistoryForTesting add null checks for currentItem()/itemAtIndex(). These are test-harness (Internals/WebKitTestRunner) paths, not attacker-reachable; test-only crash hardening.
This commit was flagged by the signal scorer and reviewed by AI (not a human). It is listed only so the triage is auditable; there is no root-cause analysis because this is not a vulnerability fix.

Structural signals: smartptr_member_added (+6.47), null_guard (+1.2), surgical (+1.3)