don't allow empty group titles

lib/frenzy_web/controllers/group_controller.ex

@@ -54,15 +54,22 @@ defmodule FrenzyWeb.GroupController do
 
   def create(conn, %{"group" => %{"title" => title}}) do
     user = conn.assigns[:user]
+    title = title |> String.trim()
 
-    changeset =
-      Ecto.build_assoc(user, :groups, %{
-        title: title
-      })
+    if String.length(title) > 0 do
+      changeset =
+        Ecto.build_assoc(user, :groups, %{
+          title: title
+        })
 
-    {:ok, group} = Repo.insert(changeset)
+      {:ok, group} = Repo.insert(changeset)
 
-    redirect(conn, to: Routes.group_path(Endpoint, :show, group.id))
+      redirect(conn, to: Routes.group_path(Endpoint, :show, group.id))
+    else
+      conn
+      |> put_flash(:error, "Group title must not be empty")
+      |> redirect(to: Routes.group_path(Endpoint, :new))
+    end
   end
 
   def delete(conn, _params) do