Fix issue in handleBatch when all records are below the minimum level, refs #203

src/Monolog/Handler/RavenHandler.php

@@ -73,6 +73,10 @@ class RavenHandler extends AbstractProcessingHandler
             return $record['level'] >= $level;
         });
 
+        if (!$records) {
+            return;
+        }
+
         // the record with the highest severity is the "main" one
         $record = array_reduce($records, function($highest, $record) {
             if($record['level'] >= $highest['level']) {