Above (line 212) you assign value to $url based on certain conditions, but here you are using that variable no matter what (so possibly it can be undefined).
If those two if statements always are going to evaluate to true then perhaps there is no point of having them, otherwise (if they evaluate to false) shouldn't that be logged?
You might be looking for something similar to this:
if ($link !== null && preg_match("/\"(.*)\"/", $link, $matches)) {
   // parsed resource loader URL
   $resourceLoaderURL = parse_url($matches[1]);
   ...
   $u->doUpdate();
} else {
   // log
}