testproject::get_by_id() Null Guard Fix

Issue #554

Fixed: calling testproject::get_by_id() with a positive id that has no matching testprojects row logged a PHP warning into the Event Viewer on every call:

E_WARNING
Trying to access array offset on null - in .../lib/functions/testproject.class.php - Line 342

The method still returned NULL (so page behavior was unaffected), but each occurrence polluted the events table — noise for administrators and risk of masking real warnings.

Root Cause

• get_by_id() resolves the project via $this->getTestProject("testprojects.id=" . intval($id), $opt).
• getTestProject() ends in return $this->db->get_recordset($sql); and database::get_recordset() initializes its output to null and returns it unchanged when the query matches zero rows (or fails).
• Line 342 then did an unguarded array dereference: return $result[0]; → under PHP 8.x, reading [0] off null raises E_WARNING: Trying to access array offset on null.
• The class's own sibling methods already guarded this exact pattern — get_by_prefix() (line ~360): return $rs != null ? $rs[0] : null; — only get_by_id() was missing the guard.

Fix Approach — mirror the existing in-class guard convention

Minimal one-line change in lib/functions/testproject.class.php (get_by_id()):

$result = $this->getTestProject($condition,$opt);
return $result != null ? $result[0] : null;

Why this way:

• Return semantics are byte-identical to before: pre-fix the method also evaluated to NULL after emitting the warning, so no caller can observe any behavioral difference except the absence of the warning. Callers already treat NULL as "project not found" (e.g. the guard added to print.inc.php initStaticRenderTestCaseForPrinting() during the #552 fix).
• Consistency over invention: reusing the same loose-comparison guard as get_by_prefix() keeps one idiom per class. Loose != null also covers the defensive cases ([], false) identically; in practice parseTestProjectRecordset() normalizes empty recordsets to null anyway.
• Alternatives rejected: changing getTestProject()'s return contract (too broad — many callers depend on it), or throwing on not-found (would be an API behavior change affecting ~85 call sites; not-found is a normal, expected outcome here).

Files Changed

File	Change
lib/functions/testproject.class.php	get_by_id(): null-guard the recordset before [0] dereference

Verification

Reproduced via PHP CLI bootstrap (testlinkInitPage($db,false,true)):

1. Pre-fix: get_by_id(99999999) → NULL + E_WARNING row appended to events (log_level=2, "Line 342").
2. Post-fix: same call → clean NULL, zero new event rows.
3. Positive path intact: get_by_id(<existing fixture>) returns the full project record (name, prefix, …).
4. Sibling methods unchanged: get_by_prefix() / get_by_name() behave as before.
5. Code review subagent over the full diff: PASS (~85 call sites audited — none index the raw result unguarded).
6. Event Viewer after all flows: 0 Error/Warning entries.

Regression suite 38 recorded in tmp/TLU_Test_Cases.md (Suite ID 45): 5/5 PASS.