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

Fixes #595

Parsedown.php

@@ -512,8 +512,6 @@ class Parsedown
     # Header
 
     protected function blockHeader($Line)
-    {
-        if (isset($Line['text'][1]))
     {
         $level = 1;
 
@@ -529,7 +527,7 @@ class Parsedown
 
         $text = trim($Line['text'], '#');
 
-            if ($this->strictMode and ( ! isset($text[0]) or $text[0] !== ' '))
+        if ($this->strictMode and isset($text[0]) and $text[0] !== ' ')
         {
             return;
         }
@@ -549,7 +547,6 @@ class Parsedown
 
         return $Block;
     }
-    }
 
     #
     # List

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 # #