fix: fatal error when using an undefined combo parameter name

[peterschade]

Problem

meth_Misc_ApplyPrmCombo is declared static but its error branch calls $this->meth_Misc_Alert(). In PHP 8 this causes a fatal error whenever a template references an undefined combo name:

Fatal error: Uncaught Error: Using $this when not in object context
  in tbs_class.php:4202

Minimal reproduction:

$tbs = new clsTinyButStrong;
$tbs->Source = '[onshow.msg;combo=undefined_combo]';
$msg = 'hello';
$tbs->Show(TBS_NOTHING); // Fatal error on PHP 8

Fix

Add an optional $TBS = null parameter to meth_Misc_ApplyPrmCombo and pass $this from the merge-time call site (meth_Locator_FindTbs). The registration-time call site (f_Misc_UpdateArray, always called with $Loc=false) stays without $TBS, so missing combos at combo-definition time are silently skipped — correct behaviour since combos can be registered in any order.

Changes

• tbs_class.php: 3-line fix in meth_Misc_ApplyPrmCombo
• testunit/testcase/PrmComboTestCase.php: new unit test case with two tests
  • testKnownCombo — verifies a registered combo's parameters are applied
  • testUnknownComboRaisesTbsError — reproduces the bug; passes only after the fix
• testunit/index.php: registers the new test case

[Skrol29]

Thanks, very well documented and the idea of the optional argument is good.
The fix is nice but the new UnitTest fails, I'm going to look into it.