tlIssueTracker::getInterfaceObject() Null Guard Fix

Issue #553

Fixed: with a test project where issue_tracker_enabled=1 but no issue tracker is linked, every code path reaching tlIssueTracker::getInterfaceObject() logged a PHP warning into the Event Viewer — e.g. single test case printing (lib/testcases/tcPrint.php → print.inc.php initStaticRenderTestCaseForPrinting()):

E_WARNING
Trying to access array offset on null - in .../lib/functions/tlIssueTracker.class.php - Line 673

The method still returned NULL afterwards (so pages kept working), but each occurrence polluted the events table.

Root Cause

• getInterfaceObject() starts with $issueT = $this->getLinkedTo($tprojectID);.
• When the project has no tracker linked (no row in testproject_issuetracker), getLinkedTo() runs a JOIN query that matches zero rows and its recordset path returns null.
• Line 673 then did an unguarded dereference: $name = $issueT['issuetracker_name']; → under PHP 8.x reading an array offset off null raises E_WARNING: Trying to access array offset on null.
• The !is_null($issueT) guard existed only further down (~line 685), after the array access had already happened.

Fix Approach — guard before first use

Minimal change at the top of getInterfaceObject() (lib/functions/tlIssueTracker.class.php):

$issueT = $this->getLinkedTo($tprojectID);
// guard: project may have issue_tracker_enabled=1 but NO tracker linked,
// then getLinkedTo() returns null and PHP8 warns on array offset access
$name = !is_null($issueT) ? $issueT['issuetracker_name'] : '';

Why this way:

• Behavior is identical to before: pre-fix the code warned, set $name to null and eventually returned $_SESSION['its'][$name] = null via the existing else-branch; post-fix it silently sets $name = '' and returns the same null interface. No caller can observe any difference except the absence of the warning.
• One guard covers all callers: all call sites share this single method — print.inc.php, execSetResults.php, resultsBugs.php, resultsByStatus.php, execHistory.php, bugAdd.php, testcaseCommands.class.php, mainPage.php, api/execute/index.php, … — fixing it here protects every screen.
• Alternatives rejected: moving the $name assignment below the existing null check would leave $name undefined on the unlinked path (isset() / session keying below uses it), and restructuring into an early return would be a larger diff for no functional gain.

Files Changed

File	Change
lib/functions/tlIssueTracker.class.php	getInterfaceObject(): compute $name with a null-safe ternary instead of dereferencing $issueT directly

Verification

Reproduced through the real browser flow against a fresh DB:

1. Fixture: project "IT553 Project" (id 1) created via UI; UPDATE testprojects SET issue_tracker_enabled=1; one test case created via UI; no tracker linked.
2. Pre-fix: open lib/testcases/tcPrint.php?testcase_id=2&tproject_id=1 → E_WARNING row appended to events (log_level=2, "Line 673").
3. Post-fix same flow → full single-TC print view renders ("Test Case IT553-1: TC for issue 553 [Version : 1]"), zero new event rows.
4. Positive path intact: link a tracker (type 15 redmine-rest) via SQL, repeat print → interface object instantiated, page renders, zero events.
5. Negative path restored (link removed): repeat print → still warning-free.
6. Event Viewer after all flows: 0 Error/Warning entries.

Regression suite 39 recorded in tmp/TLU_Test_Cases.md (Suite ID 46): 6/6 PASS.