Scrutinizer tweak

src/PhpSpreadsheet/Calculation/Calculation.php

@@ -4866,7 +4866,7 @@ class Calculation
                 }
             } elseif (preg_match('/^' . self::CALCULATION_REGEXP_FUNCTION . '$/miu', $token ?? '', $matches)) {
                 // if the token is a function, pop arguments off the stack, hand them to the function, and push the result back on
-                if ($pCellParent) {
+                if ($cell !== null && $pCellParent !== null) {
                     $cell->attach($pCellParent);
                 }