Try the following:
In TopicPrefix.integrate.php find
if (count($available_prefixes) > 1)
{
$quick_prefixes = 'var quick_prefixes = [';
foreach ($available_prefixes as $id => $value)
{
$quick_prefixes .= '{"id": ' . $id . ', "text": ' . JavaScriptEscape($value['text']) . '},';
}
}
$quick_prefixes = substr($quick_prefixes, 0, -1) . ']';
addInlineJavascript($quick_prefixes);
and replace it with
if (count($available_prefixes) > 1)
{
$quick_prefixes = 'var quick_prefixes = [';
foreach ($available_prefixes as $id => $value)
{
$quick_prefixes .= '{"id": ' . $id . ', "text": ' . JavaScriptEscape($value['text']) . '},';
}
$quick_prefixes = substr($quick_prefixes, 0, -1) . ']';
addInlineJavascript($quick_prefixes);
}