check realpath for false returns

src/bootstrap/requires.php

@@ -76,7 +76,13 @@ final class requires {
         }
         $dir = str_replace('_DS_', '/', $dir);
         $dir = self::filter_dir_path($dir);
-        $dir = escapeshellcmd(realpath($dir));
+        
+        $realpath = realpath($dir);
+        if ($realpath === false) {
+            return false;
+        }
+        
+        $dir = escapeshellcmd(realpath($realpath));
         return (file_exists($dir)) ? $dir : false;
     }