Fix bug where empty atx headings would not be recognised (CommonMark)

Fixes #595

Parsedown.php

@@ -513,42 +513,39 @@ class Parsedown
 
     protected function blockHeader($Line)
     {
-        if (isset($Line['text'][1]))
+        $level = 1;
+
+        while (isset($Line['text'][$level]) and $Line['text'][$level] === '#')
         {
-            $level = 1;
-
-            while (isset($Line['text'][$level]) and $Line['text'][$level] === '#')
-            {
-                $level ++;
-            }
-
-            if ($level > 6)
-            {
-                return;
-            }
-
-            $text = trim($Line['text'], '#');
-
-            if ($this->strictMode and ( ! isset($text[0]) or $text[0] !== ' '))
-            {
-                return;
-            }
-
-            $text = trim($text, ' ');
-
-            $Block = array(
-                'element' => array(
-                    'name' => 'h' . min(6, $level),
-                    'handler' => array(
-                        'function' => 'lineElements',
-                        'argument' => $text,
-                        'destination' => 'elements',
-                    )
-                ),
-            );
-
-            return $Block;
+            $level ++;
         }
+
+        if ($level > 6)
+        {
+            return;
+        }
+
+        $text = trim($Line['text'], '#');
+
+        if ($this->strictMode and isset($text[0]) and $text[0] !== ' ')
+        {
+            return;
+        }
+
+        $text = trim($text, ' ');
+
+        $Block = array(
+            'element' => array(
+                'name' => 'h' . min(6, $level),
+                'handler' => array(
+                    'function' => 'lineElements',
+                    'argument' => $text,
+                    'destination' => 'elements',
+                )
+            ),
+        );
+
+        return $Block;
     }
 
     #

test/data/atx_heading.html

@@ -6,7 +6,8 @@
 <h6>h6</h6>
 <p>####### not a heading</p>
 <h1>closed h1</h1>
-<p>#</p>
+<h1></h1>
+<h2></h2>
 <h1># of levels</h1>
 <h1># of levels #</h1>
 <h1>heading</h1>

test/data/atx_heading.md

@@ -16,6 +16,8 @@
 
 #
 
+##
+
 # # of levels
 
 # # of levels # #