Interpreting Gtk error message

[José Romildo Malaquias <j romildo gmail com>]

I am getting the following runtime error from an application developed
in Haskell with gtk2hs (a library binding Gtk+ to Haskell):

   (Gui:13427): Gtk-CRITICAL **: gtk_tree_view_set_cursor_on_cell:
assertion `tree_view->priv->tree != NULL' failed

What does the initial part of the message:

   Gui:13427

mean? The executable is named Gui and the source code is Gui.hs.

Romildo