check if fopen was successful before continue

lib/private/files/storage/wrapper/encryption.php

@@ -195,11 +195,15 @@ class Encryption extends Wrapper {
 	public function file_put_contents($path, $data) {
 		// file put content will always be translated to a stream write
 		$handle = $this->fopen($path, 'w');
+		if (is_resource($handle)) {
 			$written = fwrite($handle, $data);
 			fclose($handle);
 			return $written;
 		}
 
+		return false;
+	}
+
 	/**
 	 * see http://php.net/manual/en/function.unlink.php
 	 *