error-if-no-cache-control-header

Fix error on some request when Cache-Control header is missing on response

Index: ./vendor/magento/framework/App/PageCache/Kernel.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- ./vendor/magento/framework/App/PageCache/Kernel.php	(date 1591633150934)
+++ ./vendor/magento/framework/App/PageCache/Kernel.php	(date 1591633150934)
@@ -131,7 +131,9 @@
      */
     public function process(\Magento\Framework\App\Response\Http $response)
     {
-        if (preg_match('/public.*s-maxage=(\d+)/', $response->getHeader('Cache-Control')->getFieldValue(), $matches)) {
+        if ($response->getHeader('Cache-Control')
+            && preg_match('/public.*s-maxage=(\d+)/', $response->getHeader('Cache-Control')->getFieldValue(), $matches)
+        ) {
             $maxAge = $matches[1];
             $response->setNoCacheHeaders();
             if (($response->getHttpResponseCode() == 200 || $response->getHttpResponseCode() == 404)