rdbms: stop passing bogus $dbname values to DatabaseMySQL::open()

The documentation does not mention false as an accepted value

Change-Id: Iff79788884e8cc8686af08bfbde1704698b6c400

includes/installer/MysqlInstaller.php

@@ -114,7 +114,7 @@ class MysqlInstaller extends DatabaseInstaller {
 				'user' => $this->getVar( '_InstallUser' ),
 				'password' => $this->getVar( '_InstallPassword' ),
 				'ssl' => $this->getVar( 'wgDBssl' ),
-				'dbname' => false,
+				'dbname' => null,
 				'flags' => 0,
 				'tablePrefix' => $this->getVar( 'wgDBprefix' ) ] );
 			$status->setDB( $db );
@@ -378,7 +378,7 @@ class MysqlInstaller extends DatabaseInstaller {
 					'user' => $dbUser,
 					'password' => $password,
 					'ssl' => $this->getVar( 'wgDBssl' ),
-					'dbname' => false,
+					'dbname' => null,
 					'flags' => 0,
 					'tablePrefix' => $this->getVar( 'wgDBprefix' )
 				] );

includes/installer/MysqlSettingsForm.php

@@ -65,7 +65,7 @@ class MysqlSettingsForm extends DatabaseSettingsForm {
 					'user' => $this->getVar( 'wgDBuser' ),
 					'password' => $this->getVar( 'wgDBpassword' ),
 					'ssl' => $this->getVar( 'wgDBssl' ),
-					'dbname' => false,
+					'dbname' => null,
 					'flags' => 0,
 					'tablePrefix' => $this->getVar( 'wgDBprefix' )
 				] );

includes/libs/rdbms/database/DatabaseMySQL.php

@@ -138,7 +138,7 @@ class DatabaseMySQL extends Database {
 
 		try {
 			$this->currentDomain = new DatabaseDomain(
-				$db && strlen( $db ) ? $db : null,
+				( $db !== '' ) ? $db : null,
 				null,
 				$tablePrefix
 			);

includes/libs/rdbms/database/DatabaseSqlite.php

@@ -298,7 +298,7 @@ class DatabaseSqlite extends Database {
 	/**
 	 * Generates a database file name. Explicitly public for installer.
 	 * @param string $dir Directory where database resides
-	 * @param string|bool $dbName Database name (or false from Database::factory, validated here)
+	 * @param string|null $dbName Database name (or null from Database::factory, validated here)
 	 * @return string
 	 * @throws DBUnexpectedError
 	 */