Remove superfluous checks for empty realnames

src/MD_STD.php

@@ -44,7 +44,7 @@ public static function file_get_contents(string $filename):string {
     public static function realpath(string $path):string {
 
         $output = \realpath($path);
-        if (!\is_string($output) || empty($output)) {
+        if (!\is_string($output)) {
             throw new MDFileDoesNotExist("The file {$path} does not exist or is not readable.");
         }
         return $output;