[ticket/17139] Fix PHP fatal error for file transfer tool of updater

Uncaught TypeError: ftp_delete(): Argument #1 ($ftp) must be of type
FTP\\Connection, bool given
Stack trace:
#0 [ROOT]/includes/functions_transfer.php(427): ftp_delete(false, '...')

PHPBB3-17139

phpBB/includes/functions_transfer.php

@@ -341,6 +341,11 @@ class ftp extends transfer
 	*/
 	function _mkdir($dir)
 	{
+		if (!$this->connection)
+		{
+			return false;
+		}
+
 		return @ftp_mkdir($this->connection, $dir);
 	}
 
@@ -350,6 +355,11 @@ class ftp extends transfer
 	*/
 	function _rmdir($dir)
 	{
+		if (!$this->connection)
+		{
+			return false;
+		}
+
 		return @ftp_rmdir($this->connection, $dir);
 	}
 
@@ -359,6 +369,11 @@ class ftp extends transfer
 	*/
 	function _rename($old_handle, $new_handle)
 	{
+		if (!$this->connection)
+		{
+			return false;
+		}
+
 		return @ftp_rename($this->connection, $old_handle, $new_handle);
 	}
 
@@ -368,6 +383,11 @@ class ftp extends transfer
 	*/
 	function _chdir($dir = '')
 	{
+		if (!$this->connection)
+		{
+			return false;
+		}
+
 		if ($dir && $dir !== '/')
 		{
 			if (substr($dir, -1, 1) == '/')
@@ -385,6 +405,11 @@ class ftp extends transfer
 	*/
 	function _chmod($file, $perms)
 	{
+		if (!$this->connection)
+		{
+			return false;
+		}
+
 		if (function_exists('ftp_chmod'))
 		{
 			$err = @ftp_chmod($this->connection, $perms, $file);
@@ -406,6 +431,11 @@ class ftp extends transfer
 	*/
 	function _put($from_file, $to_file)
 	{
+		if (!$this->connection)
+		{
+			return false;
+		}
+
 		// We only use the BINARY file mode to cicumvent rewrite actions from ftp server (mostly linefeeds being replaced)
 		$mode = FTP_BINARY;
 
@@ -425,6 +455,11 @@ class ftp extends transfer
 	*/
 	function _delete($file)
 	{
+		if (!$this->connection)
+		{
+			return false;
+		}
+
 		return @ftp_delete($this->connection, $file);
 	}
 
@@ -449,6 +484,11 @@ class ftp extends transfer
 	*/
 	function _cwd()
 	{
+		if (!$this->connection)
+		{
+			return false;
+		}
+
 		return @ftp_pwd($this->connection);
 	}
 
@@ -458,6 +498,11 @@ class ftp extends transfer
 	*/
 	function _ls($dir = './')
 	{
+		if (!$this->connection)
+		{
+			return false;
+		}
+
 		$list = @ftp_nlist($this->connection, $dir);
 
 		// See bug #46295 - Some FTP daemons don't like './'
@@ -498,6 +543,11 @@ class ftp extends transfer
 	*/
 	function _site($command)
 	{
+		if (!$this->connection)
+		{
+			return false;
+		}
+
 		return @ftp_site($this->connection, $command);
 	}
 }