Fix Phpstan Errors

Author: oleibman

tests/PhpSpreadsheetTests/SpreadsheetCopyCloneTest.php

@@ -49,8 +49,8 @@ public function testCopyClone(string $type): void
         } else {
             $this->spreadsheet2 = clone $this->spreadsheet;
         }
-        self::assertSame($this->spreadsheet, $this->spreadsheet->getCalculationEngine()->getSpreadsheet());
-        self::assertSame($this->spreadsheet2, $this->spreadsheet2->getCalculationEngine()->getSpreadsheet());
+        self::assertSame($this->spreadsheet, $this->spreadsheet->getCalculationEngine()?->getSpreadsheet());
+        self::assertSame($this->spreadsheet2, $this->spreadsheet2->getCalculationEngine()?->getSpreadsheet());
         self::assertSame('A3', $sheet->getSelectedCells());
         $copysheet = $this->spreadsheet2->getActiveSheet();
         self::assertSame('A3', $copysheet->getSelectedCells());
@@ -132,6 +132,7 @@ public function testCopyClone2(string $type, bool $suppress, bool $cache, bool $
     {
         $this->spreadsheet = new Spreadsheet();
         $calc = $this->spreadsheet->getCalculationEngine();
+        self::assertNotNull($calc);
         $calc->setSuppressFormulaErrors($suppress);
         $calc->setCalculationCacheEnabled($cache);
         $calc->setBranchPruningEnabled($pruning);
@@ -142,6 +143,7 @@ public function testCopyClone2(string $type, bool $suppress, bool $cache, bool $
             $this->spreadsheet2 = clone $this->spreadsheet;
         }
         $calc2 = $this->spreadsheet2->getCalculationEngine();
+        self::assertNotNull($calc2);
         self::assertSame($suppress, $calc2->getSuppressFormulaErrors());
         self::assertSame($cache, $calc2->getCalculationCacheEnabled());
         self::assertSame($pruning, $calc2->getBranchPruningEnabled());