Pass context array key as string at validate0101()

[boryn]

MessageValidator fails when we use an array with keys as integers as the context. Let's look at the example:

$files[] = 'file_0.php';
$files[] = 'file_1.php';

Log::info("Files", $files);

then, preg_match() complains it needs the second argument to be a string at validate0101() in MessageValidator

[PDXfoster]

Has anyone looked at this? It's a simple fix, and is causing a major headache.