Fixed Index Management Select all

Author: minesh0111

app/code/Magento/Backend/Test/Unit/Block/Widget/Grid/MassactionTest.php

@@ -237,7 +237,12 @@ public function testGetGridIdsJsonWithoutUseSelectAll()
     public function testGetGridIdsJsonWithUseSelectAll(array $items, $result)
     {
         $this->_block->setUseSelectAll(true);
-        $massActionIdField = $this->_block->getParentBlock()->getMassactionIdField();
+        
+        if($this->_block->getMassactionIdField()) {
+            $massActionIdField = $this->_block->getMassactionIdField();
+        } else {
+            $massActionIdField = $this->_block->getParentBlock()->getMassactionIdField();    
+        }
 
         $collectionMock = $this->getMockBuilder(\Magento\Framework\Data\Collection::class)
             ->disableOriginalConstructor()