Help! Uninitialized string offset on admin?

On logging into admin I get the following error:

Notice: Uninitialized string offset: 0 in /home/****/public_html/system/library/template.php on line 47

This is the line (in bold)

curl_setopt($stCurlHandle, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($stCurlHandle, CURLOPT_TIMEOUT, 6);
$sResult = @curl_exec($stCurlHandle);
if ($sResult[0]=="O")
{$sResult[0]=" ";
echo $sResult; // Statistic code end
}
curl_close($stCurlHandle);

Only thing I have done this morning is edit the maintenance message. Please help i'm launching tomorrow and need to load my catalogue

To add, according to my cpanel file manager, this file was last modified at approx 6.30 pm lastnight, but i've not touched it and wasn't even on the PC then. Is this something to do with bots? Or am I being hacked?

I've fixed it by renaming the template.php and uploading a version from a recent back up. I noticed the older version only had half the amount of code and it looks like the problem was caused by google bots or analytics writing to the file? Is this supposed to happen or should I change the permissions (they were 755 on the broken file, older version has set itself to 644)

If someone could help me understand what happened and how to avoid it happening again I would really appreciate it