Fix error of debug page

Error occurred when $messages variable is null and this exception throw:

Invalid argument supplied for foreach()

close #73

Author: jafaripur

CHANGELOG.md

@@ -10,6 +10,7 @@ Yii Framework 2 elasticsearch extension Change Log
 - Bug #19: `DeleteAll` now deletes all entries, not first 10 (beowulfenator)
 - Bug #48: `UpdateAll` now updates all entries, not first 10 (beowulfenator)
 - Bug #65: Fixed warning `array to string conversion` when parsing error response (rhertogh, silverfire)
+- Bug #73: Fixed debug panel exception when no data was recorded for elasticsearch panel (jafaripur)
 - Enh #2: Added `min_score` option to query (knut)
 - Enh #28: AWS Elasticsearch service compatibility (andrey-bahrachev)
 - Enh #33: Implemented `Command::updateSettings()` and `Command::updateAnalyzers()` (githubjeka)

DebugPanel.php

@@ -157,7 +157,7 @@ public function calculateTimings()
         if ($this->_timings !== null) {
             return $this->_timings;
         }
-        $messages = $this->data['messages'];
+        $messages = isset($this->data['messages']) ? $this->data['messages'] : [];
         $timings = [];
         $stack = [];
         foreach ($messages as $i => $log) {