Fix a couple bugs.

mwparserfromhell/wikicode.py

@@ -370,7 +370,7 @@ class Wikicode(StringMixIn):
             if self.nodes[i] in headings:
                 this = self.nodes[i].level
                 for (level, start) in buffers:
-                    if not flat or this <= level:
+                    if this <= level:
                         buffers.remove((level, start))
                         sections.append(Wikicode(self.nodes[start:i]))
                 buffers.append((this, i))

tests/test_wikicode.py

@@ -305,8 +305,8 @@ Even more text.
 An invalid section!"""
 
         self.assertEqual([], parse(page1).get_sections())
-        self.assertEqual(["==Heading=="], parse(page2).get_sections())
-        self.assertEqual(["===Heading===\nFoo bar baz\n", "====Gnidaeh====\n"], parse(page2).get_sections())
+        self.assertEqual(["", "==Heading=="], parse(page2).get_sections())
+        self.assertEqual(["", "===Heading===\nFoo bar baz\n====Gnidaeh====\n", "====Gnidaeh====\n"], parse(page3).get_sections())
 
     def test_strip_code(self):
         """test Wikicode.strip_code()"""