Bugfix Issue 1333 tcCompareVersions BuildDiff Foreach Null

Bugfix — Issue #1333: Legacy tcCompareVersions — buildDiff() foreach on null input fires E_WARNING

Problem

Submitting a compare on the LEGACY page lib/testcases/tcCompareVersions.php with testcase_id=0 (or any project-scoped request where the testcase lookup returns no versions) fires E_WARNING Invalid argument supplied for foreach() at buildDiff() (Line 157 area). The HTTP response stays 200; the symptom is only visible in the Event Viewer / events table (log_level=2, activity=PHP).

Reproduce at HEAD (measured on the fresh-import CI box): with an authenticated session call

curl -b <cookies> ".../lib/testcases/tcCompareVersions.php?tproject_id=1&testcase_id=0&compare_selected_versions=1"

→ HTTP 200 + one E_WARNING\nInvalid argument supplied for foreach() row per request.

Root Cause

• init_args() sets $args->tcase_id = intval($_REQUEST['testcase_id'] ?? 0) → 0.
• getTestcaseVersions() / the compare handler feed buildDiff() with $items = null when the testcase has no candidate versions, and buildDiff() iterates it unconditionally:

foreach ($items as $item) { ... }

• PHP 8 throws Invalid argument supplied for foreach() for null, logging the warning to events.

Blast radius: file-local. The dashio Smarty template tolerates an empty diff (renders the selection form fine). The modern tcCompare.html screen (Refs #809/#1327, BFF api/testcasescompare/index.php) is unaffected — it has its own guards.

Fix

Committed on the default branch as part of the #1333 run, commit 1f2d0a5d3:

public function buildDiff($items, $fieldNames) {
  $diff = array();
  if (!is_array($items)) {
    return $diff;
  }
  foreach ($items as $item) { ... }
}

Early-return on non-array input — no more foreach warning, and the page keeps rendering the "select versions" form exactly as before. No new user-facing strings → no locale-bundle additions.

Files Changed

• lib/testcases/tcCompareVersions.php — buildDiff(): is_array() guard.
• tmp/TLU_Test_Cases.md — regression suite "Regression — Issues #1333/#1329/#1340/#1341", 17/17 PASS.

Verification

All checks on the fresh-import CI box, admin session:

• Pre-fix repro via curl = 1 E_WARNING row (Invalid argument supplied for foreach).
• Post-fix same URL = HTTP 200, 0 new log_level IN (2,3) rows.
• Happy path compare (testcase_id=3&version_left=1&version_right=2&compare_selected_versions=1) still renders the diff.
• Event Viewer after the pass: only INFO/AUDIT (audit_login_succeeded).

Address: Fixes #1333 (pushed on the default branch; issue auto-closes on merge).