MCP-903: Fix default connection = db setting after Magento installation

- Do not write lock/config/prefix=null to env.php;

Author: adifucan

lib/internal/Magento/Framework/Lock/Backend/Database.php

@@ -162,7 +162,7 @@ private function addPrefix(string $name): string
      */
     private function getPrefix(): string
     {
-        if ($this->prefix === null || $this->prefix === '') {
+        if ($this->prefix === null) {
             $this->prefix = (string)$this->deploymentConfig->get(
                 ConfigOptionsListConstants::CONFIG_PATH_DB_CONNECTION_DEFAULT
                 . '/'

setup/src/Magento/Setup/Model/ConfigOptionsList/Lock.php

@@ -134,7 +134,6 @@ class Lock implements ConfigOptionsListInterface
      */
     private $defaultConfigValues = [
         self::INPUT_KEY_LOCK_PROVIDER => LockBackendFactory::LOCK_DB,
-        self::INPUT_KEY_LOCK_DB_PREFIX => null,
         self::INPUT_KEY_LOCK_ZOOKEEPER_PATH => ZookeeperLock::DEFAULT_PATH,
     ];
 
@@ -317,7 +316,10 @@ private function setDefaultConfiguration(
         string $lockProvider
     ) {
         foreach ($this->mappingInputKeyToConfigPath[$lockProvider] as $input => $path) {
-            $configData->set($path, $deploymentConfig->get($path, $this->getDefaultValue($input)));
+            // do not set default value null for lock db prefix
+            if ($input !== self::INPUT_KEY_LOCK_DB_PREFIX) {
+                $configData->set($path, $deploymentConfig->get($path, $this->getDefaultValue($input)));
+            }
         }
 
         return $configData;
@@ -333,10 +335,6 @@ private function setDefaultConfiguration(
      */
     private function getDefaultValue(string $inputKey)
     {
-        if (isset($this->defaultConfigValues[$inputKey])) {
-            return $this->defaultConfigValues[$inputKey];
-        } else {
-            return null;
-        }
+        return $this->defaultConfigValues[$inputKey] ?? null;
     }
 }