move parent[] to parent as the array was never needed, removed some dead code, clarified another example of new BUG-46

templates/books_for_series.html

@@ -6,7 +6,7 @@
 		{% for book in books %}
 		<tr>
 			<td id="{{book.id}}">
-				{% if book.parent|length %}
+				{% if book.parent %}
 					{% set style="style=visibility:hidden" %}
 				{% endif %}
 				<button name="move_button" value="up-{{book.id}}" id="up-{{book.id}}" class="btn btn-outline-primary btn-small" {{style}}
@@ -51,8 +51,8 @@
 				{% endif %}
 				{% if SeriesBookNum( s.id, book.id ) == 1 %}
 					<script>
-						{% if book.parent|length %}
-							$('#up-{{book.parent[0].id}}').prop("disabled", true)
+						{% if book.parent %}
+							$('#up-{{book.parent.id}}').prop("disabled", true)
 						{% else %}
 							$('#up-{{book.id}}').prop("disabled", true)
 						{% endif %}
@@ -60,8 +60,8 @@
 				{% endif %}
 				{% if SeriesBookNum( s.id, book.id ) == s.num_books %} 
 					<script>
-						{% if book.parent|length %}
-							$('#down-{{book.parent[0].id}}').prop("disabled", true)
+						{% if book.parent %}
+							$('#down-{{book.parent.id}}').prop("disabled", true)
 						{% else %}
 							$('#down-{{book.id}}').prop("disabled", true)
 						{% endif %}