Fix corpus build process

app/models.py

@@ -875,7 +875,9 @@ class Corpus(HashidMixin, db.Model):
             text_element.set('publishing_year', str(corpus_file.publishing_year))  # noqa
             text_element.set('school', corpus_file.school or 'NULL')
             text_element.set('title', corpus_file.title)
-            corpus_element.insert(1, text_element)
+            text_element.tail = '\n'
+            # corpus_element.insert(1, text_element)
+            corpus_element.append(text_element)
         ET.ElementTree(corpus_element).write(
             os.path.join(self.path, 'cwb', 'corpus.vrt'),
             encoding='utf-8'