Minor Issue with generating JS/CSS compressed files

There is an issue on some hosting server with generating JS/CSS compressed files. This issue is related to recent improvement which adds ability to use JAVA Class to do a better compression.

The following code haven't full worked as expected on examined hosting server:

[code]
$command = 'java -jar ' . dirname(_FILE_) . DIRECTORY_SEPARATOR . 'yuicompressor-2.4.2.jar --type ' . $extension . ' --charset utf-8 ' . $tmp_file;

$compressed_string = shell_exec($command);

unlink($tmp_file);

if (!is_null($compressed_string))

[/code]

The solution is to add check if $compressed_string has any length.