LIMS-2141: Suppress errors if visit directory has been replaced with a file

[ndg63276]

JIRA ticket: LIMS-2141

Summary:

If the whole visit folder (or any folder in the path of an expected file) has been replaced with a file, then the combination of file_exists and open_basedir cause an error. See eg https://ispyb.diamond.ac.uk/dc/visit/cm40636-1

Changes:

• Use the @ operator to suppress errors on file_exist calls on the data collection page

To test:

• Deploy to a full server with open_basedir set, then go to /dc/visit/cm40636-1. Check there are no errors.

Alternatives:
The other option would be to manually check all paths for directories replaced by files, eg

function safe_file_exists($fullPath) {
    $parts = explode('/', trim($fullPath, '/'));
    $current = '';
    foreach ($parts as $part) {
        $current .= '/' . $part;
        if ($current !== $fullPath) {
            if (!is_dir($current)) {
                return false;
            }
        }
    }
    return file_exists($fullPath);
}

But that seemed to be slower by a factor of 5-10x, and could result in a lot of extra calls to the metadata server.