[fix] correct redirection when only chapter in url

crenum.py

@@ -12,7 +12,7 @@ def index():
     return render_template('index.html.j2')
 
 @app.route('/book<bookNb>')
-# @app.route('/book<bookNb>/<chapName>')
+@app.route('/book<bookNb>/<chapName>')
 @app.route('/book<bookNb>/<chapName>/<visu>')
 @app.route('/book<bookNb>/<chapName>/p<pageNb>')
 @app.route('/book<bookNb>/<chapName>/p<pageNb>/<visu>')