Description:
Upon creating any images in the program and trying to edit some of the parameters in the GUI the following errors are attained:

(synfigstudio:6060): Gtk-CRITICAL **: gtk_tree_view_column_cell_process_action: assertion 'GTK_IS_CELL_EDITABLE (*editable_widget)' failed

(synfigstudio:6060): GLib-GObject-WARNING **: When installing property: type 'gtkmm__CustomObject_N6studio15ValueBase_EntryE' already has a property named 'editing-canceled'

(synfigstudio:6060): GLib-GObject-WARNING **: attempting to add an interface (GtkCellEditable) to class (gtkmm__CustomObject_N6studio15ValueBase_EntryE) after class_init

(synfigstudio:6060): GLib-GObject-WARNING **: gsignal.c:2461: signal 'editing_done' is invalid for instance '0x9d91560' of type 'gtkmm__CustomObject_N6studio15ValueBase_EntryE'


Additional info:
* More information on synfig bug report site: http://www.synfig.org/issues/thebuggenie/synfig/issues/699
* Possible fix also listed there.


Steps to reproduce:
Open program, draw any simple shape on the canvas, go to the "Parameters, Library, Keyframes, Timetrack, Graphs, Canvas MetaData" window and try to modify any of the properties for the object (example: 'amount') -- property remains uneditable and errors occur on command line.