Issue #80 add is_int($param) to $commentid loop

lib.php

@@ -425,7 +425,7 @@ function pdfannotator_pluginfile($course, $cm, $context, $filearea, $args, $forc
     if ($filearea === 'post') {
         $commentid = 0;
         foreach ($args as $param) {
-            if ($DB->record_exists('pdfannotator_comments', ['id' => $param])) {
+            if (is_int($param) && $DB->record_exists('pdfannotator_comments', ['id' => $param])) {
                 $commentid = $param;
                 break;
             }