hint to a missing markdown=1 attribute

revert adding "frame" to void-elements

Author: Chaosmeister

vendor/erusev/parsedown-extra/ParsedownExtra.php

@@ -635,6 +635,7 @@ protected function processTag($elementMarkup) # recursive
         if ($errors)
         {
             $errormessage = "<h1>HTML-parser error:</h1><br>";
+            $errormessage .= "The input was interpret as HTML - did you miss the <code>markdown=1</code> attribute?<br>";
             foreach ($errors as $error) {
                 $errormessage .= "Line: " . $error->line . " - " . $error->message;
                 $errormessage .= '<br>';
@@ -645,6 +646,7 @@ protected function processTag($elementMarkup) # recursive
         if (!isset($DOMDocument->firstChild->firstChild->firstChild))
         {
             $errormessage = "<h1>General HTML-parser error:</h1><br>";
+            $errormessage .= "The input was interpret as HTML - did you miss the <code>markdown=1</code> attribute?<br>";
             $errormessage .= "Input:<pre><code>" . htmlspecialchars($elementMarkup) . "</code></pre>";
             $errormessage .= "Output:<pre><code>" . htmlspecialchars($DOMDocument->saveHTML()) . "</code></pre>";
             return $errormessage;

vendor/erusev/parsedown/Parsedown.php

@@ -1977,7 +1977,7 @@ static function instance($name = 'default')
     protected $regexHtmlAttribute = '[a-zA-Z_:][\w:.-]*+(?:\s*+=\s*+(?:[^"\'=<>`\s]+|"[^"]*+"|\'[^\']*+\'))?+';
 
     protected $voidElements = array(
-        'area', 'base', 'br', 'col', 'command', 'embed', 'hr', 'img', 'input', 'link', 'meta', 'param', 'source', 'frame'
+        'area', 'base', 'br', 'col', 'command', 'embed', 'hr', 'img', 'input', 'link', 'meta', 'param', 'source'
     );
 
     protected $textLevelElements = array(