fix problems with header that look falsy. fixes #1770

_test/tests/inc/parser/renderer_xhtml.test.php

@@ -248,4 +248,20 @@ class renderer_xhtml_test extends DokuWikiTest {
 ';
         $this->assertEquals($expected, $this->R->doc);
     }
+
+    public function test_blankHeader() {
+        $this->R->header('0', 1, 1);
+        $expected = '<h1 class="sectionedit1" id="section0">0</h1>';
+        $this->assertEquals($expected, trim($this->R->doc));
+    }
+
+    public function test_blankTitleLink() {
+        global $conf;
+        $conf['useheading'] = 1;
+        saveWikiText('test','====== 0 ======', 'test');
+        $this->R->internallink('test');
+
+        $expected = '<a href="/./doku.php?id=test" class="wikilink1" title="test">0</a>';
+        $this->assertEquals($expected, trim($this->R->doc));
+    }
 }

inc/parser/xhtml.php

@@ -191,7 +191,7 @@ class Doku_Renderer_xhtml extends Doku_Renderer {
     function header($text, $level, $pos) {
         global $conf;
 
-        if(!$text) return; //skip empty headlines
+        if(blank($text)) return; //skip empty headlines
 
         $hid = $this->_headerToLink($text, true);
 
@@ -1688,7 +1688,7 @@ class Doku_Renderer_xhtml extends Doku_Renderer {
         } elseif(is_null($title) || trim($title) == '') {
             if(useHeading($linktype) && $id) {
                 $heading = p_get_first_heading($id);
-                if($heading) {
+                if(!blank($heading)) {
                     return $this->_xmlEntities($heading);
                 }
             }