filemtime(): stat failed for /var/www/clients/client2/web1/web/themes/default/css/FFAHM/FFAHM.styles.css
http://elkarte.sch.my/index.php?action=admin;area=packages;sa=uninstall2;package=FFAHM.v.112.elkarte.ahrasis.com.zip;pid=208
File: /var/www/clients/client2/web1/web/sources/SiteCombiner.class.php
263:				$filename = $options['dir'] . $options['basename'];
264:				$this->_combine_files[$options['basename']] = array(
265:					'file' => $filename,
266:					'basename' => $options['basename'],
267:					'url' => $options['url'],
==>268:					'filemtime' => filemtime($filename),
269:					'minimized' => (bool) strpos($options['basename'], '.min.js') !== false || strpos($options['basename'], '.min.css') !== false,
270:				);
file_get_contents(/var/www/clients/client2/web1/web/themes/default/css/FFAHM/FFAHM.styles.css): failed to open stream: No such file or directory
http://elkarte.sch.my/index.php?action=admin;area=packages;sa=uninstall2;package=FFAHM.v.112.elkarte.ahrasis.com.zip;pid=208
File: /var/www/clients/client2/web1/web/sources/SiteCombiner.class.php
341:			// Read in all the data so we can process
342:			foreach ($this->_combine_files as $key => $file)
343:			{
==>344:				$tempfile = trim(file_get_contents($file['file']));
345:				$tempfile = (substr($tempfile, -3) === '}()') ? $tempfile . ';' : $tempfile;
346:				$this->_combine_files[$key]['content'] = $tempfile;
The above only happens while uninstalling FFAHM addon i.e. hooking the following code into integrate_admin_areas: 
	global $modSettings;
	// Add style(s)	
	if (!empty($modSettings['ffahm_enable']))
		loadCSSFile('FFAHM/FFAHM.styles.css');
After several tests, I managed to get it working, installed and uninstalled without errors by putting a full url instead of path from css path as follows:
	global $modSettings, $settings;
	// Add style(s)	
	if (!empty($modSettings['ffahm_enable']))
		loadCSSFile($settings['default_theme_url'] . '/css/FFAHM/FFAHM.styles.css');
Oddly, my other addons doesn't face the same error though load css in a very similar way.
Any explanation or correction for this?