Don't cause http 500 if no label is chosen

todosrht/blueprints/ticket.py

@@ -320,6 +320,18 @@ def ticket_add_label(owner, name, ticket_id):
     if not TicketAccess.edit in access:
         abort(401)
 
+    valid = Validation(request)
+    label_id = valid.require("label_id", friendly_name="A label")
+    if not valid.ok:
+        return render_template("ticket.html",
+            tracker=tracker, ticket=ticket, access=access, **valid.kwargs)
+
+    valid.expect(re.match(r"^\d+$", label_id),
+            "Label ID must be numeric", field="label_id")
+    if not valid.ok:
+        return render_template("ticket.html",
+            tracker=tracker, ticket=ticket, access=access, **valid.kwargs)
+
     label_id = int(request.form.get('label_id'))
     label = Label.query.filter(Label.id == label_id).first()
     if not label:

todosrht/templates/ticket.html

@@ -141,8 +141,12 @@
                 ticket_id=ticket.scoped_id,
               )
             }}">
-            <select id="label_id" name="label_id" class="form-control">
-              <option>-- Pick one --</option>
+            <select
+              id="label_id"
+              name="label_id"
+              class="form-control {{ valid.cls("label_id") }}"
+            >
+              <option value="">-- Pick one --</option>
               {% for label in tracker.labels if label not in ticket.labels %}
               <option
                 value="{{ label.id }}"
@@ -155,6 +159,7 @@
             <button type="submit" class="btn btn-default">
               Add label {{icon('caret-right')}}
             </button>
+            {{ valid.summary('label_id') }}
           </form>
         </dd>
         {% else %}