Cannot write empty configuration

[tiborb]

When I attempt to write an empty config to a file (say, I removed the last remaining section) using Supervisor\Configuration\Writer\File it will throw a [Supervisor\Exception\WrittingFailed] Cannot write configuration into file /path/to/file.conf exception.

Storing an empty string to a file $this->writeFile($fileContents)) will return 0, this in turen gets evaluates as false, and an exception will be thrown:

if (!$result = $this->writeFile($fileContents)) {
            throw new WrittingFailed(sprintf('Cannot write configuration into file %s', $this->file));
        }

Even though the write operation was successful.
Non boolean value go evaluated to false, a check for boolean false fixes this issue:

if (false === $result = $this->writeFile($fileContents)) {
            throw new WrittingFailed(sprintf('Cannot write configuration into file %s', $this->file));
        }

More details: http://php.net/manual/en/function.file-put-contents.php