Description of problem:
* In Gnome Boxes create a new Box
* Select a File
* in the Gnome Boxes dialog select a folder
* switch to Nautilus, navigate to the same folder
* in nautilus rename a file so that it has a .iso ending

Note: I also tested if inserting a iso file to this folder in nautilus would also result in a crash, but in this case it doesn't. A existing non-iso file has to be renamed, to apear as iso file; then it crashs.

Version-Release number of selected component:
gnome-boxes-3.6.2-1.fc18

Additional info:
backtrace_rating: 4
cmdline:        gnome-boxes
executable:     /usr/bin/gnome-boxes
kernel:         3.6.7-5.fc18.x86_64
remote_result:  831444

Truncated backtrace:
Thread no. 1 (10 frames)
 #4 _gtk_rbtree_insert_after at gtkrbtree.c:465
 #5 gtk_tree_view_row_inserted at gtktreeview.c:8871
 #10 gtk_tree_model_row_inserted at gtktreemodel.c:1821
 #11 emit_row_inserted_for_node at gtkfilesystemmodel.c:309
 #12 node_set_visible_and_filtered_out at gtkfilesystemmodel.c:359
 #13 node_compute_visibility_and_filters at gtkfilesystemmodel.c:481
 #14 add_file at gtkfilesystemmodel.c:1867
 #15 _gtk_file_system_model_update_file at gtkfilesystemmodel.c:1941
 #16 gtk_file_system_model_query_done at gtkfilesystemmodel.c:1226
 #17 g_simple_async_result_complete at gsimpleasyncresult.c:775