Fix false cache_lifetime usage in xml layouts #16086

Author: VladimirZaets

lib/internal/Magento/Framework/View/Element/AbstractBlock.php

@@ -1064,14 +1064,10 @@ protected function getCacheTags()
     /**
      * Get block cache life time
      *
-     * @return int|bool|null
+     * @return int|null
      */
     protected function getCacheLifetime()
     {
-        if (!$this->hasData('cache_lifetime')) {
-            return null;
-        }
-
         $cacheLifetime = $this->getData('cache_lifetime');
         if (false === $cacheLifetime || null === $cacheLifetime) {
             return null;

lib/internal/Magento/Framework/View/Test/Unit/Element/AbstractBlockTest.php

@@ -287,15 +287,6 @@ public function getCacheLifetimeDataProvider()
                 'expectsCacheSave' => $this->never(),
                 'expectedResult' => '',
             ],
-            [
-                'cacheLifetime' => false,
-                'dataFromCache' => 'dataFromCache',
-                'dataForSaveCache' => '',
-                'expectsDispatchEvent' => $this->exactly(2),
-                'expectsCacheLoad' => $this->once(),
-                'expectsCacheSave' => $this->never(),
-                'expectedResult' => 'dataFromCache',
-            ],
             [
                 'cacheLifetime' => 120,
                 'dataFromCache' => 'dataFromCache',