fix (new) BUG where removing a parent book from a series caused error with bsl-book-num missing. Also flagged 2 spots for dealing with removing parent/child books from a series better, and stopped any attempt to for now

templates/book.html

@@ -249,6 +249,7 @@ function AddAuthorToBook(num) {
 								Book {{ SeriesBookNum( s.id, books.id ) }} of {{s.num_books}} in&nbsp; <a href=/series/{{s.id}}>{{s.title}}</a>
 							</div>
 						{% else %}
+							{% set hiddens.txt=hiddens.txt+"<input type='hidden' name='bsl-book_num-{}' value='PARENT'>".format(loop.index) %}
 							<div id="series-minus-div-{{loop.index}}" class="input-group-prepend">
 								<button id="series-minus-but-{{loop.index}}" class="btn btn-outline-danger" type="button" onClick="RemoveBookFromSeries('series-div-{{loop.index}}')">
 									<i class="fas fa-minus"></i>