Hi i am trying to add a custom import fucntionality for my module but I got this error:-
Fatal error: Uncaught Error: Call to a member function getUrl() on null in E:\xampp\htdocs\m2\vendor\magento\framework\View\Element\AbstractBlock.php:775 Stack trace: #0 E:\xampp\htdocs\m2\vendor\magento\module-backend\Block\Widget\Tabs.php(141): Magento\Framework\View\Element\AbstractBlock->getUrl() #1 [internal function]: Magento\Backend\Block\Widget\Tabs->addTab('importpincode', 'netsmartz_pinco...') #2 E:\xampp\htdocs\m2\vendor\magento\framework\View\Layout\Generator\Block.php(298): call_user_func_array(Array, Array) #3 E:\xampp\htdocs\m2\vendor\magento\framework\View\Layout\Generator\Block.php(169): Magento\Framework\View\Layout\Generator\Block->generateAction(Object(Netsmartz\PincodeChecker\Block\Adminhtml\Importpincode\Edit\Tabs), 'addTab', Array) #4 E:\xampp\htdocs\m2\vendor\magento\framework\View\Layout\GeneratorPool.php(81): Magento\Framework\View\Layout\Generator\Block->process(Object(Magento\Framework\View\Layout\Reader\Context), Object(Magento\Framework\View\Layout\Generator\Context)) #5 E:\xampp\htdocs\m2\ve in E:\xampp\htdocs\m2\vendor\magento\framework\View\Element\AbstractBlock.php on line 775
here is my code:-
<?php namespace vendor\module\Block\Adminhtml\Importpincode\Edit\Tab; class Importpincode extends \Magento\Backend\Block\Widget\Form\Generic implements \Magento\Backend\Block\Widget\Tab\TabInterface { protected $_assetRepo; public function __construct( \Magento\Framework\View\Asset\Repository $assetRepo ) { $this->_assetRepo = $assetRepo; } /** * Prepare form * * @return $this */ protected function _prepareForm() { $path = $this->_assetRepo->getUrl("vendor_module::importsample/sample.csv"); $form = $this->_formFactory->create(); $objectManager = \Magento\Framework\App\ObjectManager::getInstance(); $storemanager = $objectManager->create('Magento\Store\Model\StoreManagerInterface'); $fieldset = $form->addFieldset( 'base_fieldset', [ 'legend' => __('Import Pincodes'), 'class' => 'fieldset-wide' ] ); $importdata_script = $fieldset->addField( 'file', 'file', [ 'name' => 'file', 'label' => __('Upload File'), 'title' => __('Upload File'), 'required' => true, ] ); $importdata_script->setAfterElementHtml(" <span id='sample-file-span' ><a id='sample-file-link' href='".$path."' >Download Sample File</a></span> "); $this->setForm($form); return parent::_prepareForm(); } /** * Prepare label for tab * * @return string */ public function getTabLabel() { return __('Import Pincodes'); } /** * Prepare title for tab * * @return string */ public function getTabTitle() { return $this->getTabLabel(); } /** * Can show tab in tabs * * @return boolean */ public function canShowTab() { return true; } /** * Tab is hidden * * @return boolean */ public function isHidden() { return false; } } any help on this will be great
update:- 
