Use empty() over === false to also return error in case of empty strings

src/MD_STD_IN.php

@@ -96,7 +96,7 @@ public static function sanitize_text(mixed $input):string {
      */
     public static function sanitize_rgb_color(mixed $input):string {
 
-        if (($output = \filter_var($input, FILTER_UNSAFE_RAW, FILTER_FLAG_STRIP_LOW | FILTER_FLAG_STRIP_HIGH)) === false) {
+        if (empty($output = \filter_var($input, FILTER_UNSAFE_RAW, FILTER_FLAG_STRIP_LOW | FILTER_FLAG_STRIP_HIGH))) {
             throw new MDInvalidColorCode("Invalid color code provided: " . $output);
         }