You can find the problem expressions by running the following command from your Magento 2 root folder:
grep -rnw . -e "__('')" -e '__("")'
The output for your store:
./app/code/Magestore/Affiliateplus/view/frontend/templates/account/program.phtml:84: $commissionText = $block->formatPrice($commission) . ’ ’ . __(‘’);
./app/code/Magestore/Affiliateplus/view/frontend/templates/account/program.phtml:91: $secText = $block->formatPrice($secCommission) . ’ ’ . __(‘’);
./app/code/Magestore/Affiliateplus/view/frontend/templates/payment/moneybooker.phtml:69: <?php echo __('') ?>
./app/code/Magestore/Affiliateplus/view/frontend/templates/payment/paypal.phtml:65: <?php echo __('') ?>
As you can see, the problem is because of the «Magestore Affiliateplus» extension.
Report the bug to the extension’s developer.