Don't add empty method to the cart summary

In some cases the method html is empty, this will result in an empty
list item, which in the end results in an extra margin of 20px because
of default styling.

Author: arnoudhgz

app/code/Magento/Checkout/view/frontend/templates/cart/methods.phtml

@@ -14,7 +14,8 @@
 <?php $methods = $block->getMethods('methods') ?: $block->getMethods('top_methods') ?>
 <ul class="checkout methods items checkout-methods-items">
 <?php foreach ($methods as $method): ?>
-    <?php if ($methodHtml = $block->getMethodHtml($method)): ?>
+    <?php $methodHtml = $block->getMethodHtml($method); ?>
+    <?php if (trim($methodHtml) !== ''): ?>
     <li class="item"><?= /* @escapeNotVerified */ $methodHtml ?></li>
     <?php endif; ?>
 <?php endforeach; ?>