fix some compile warnings



to avoid those build warnings.

fm-directory-view.c: In function 'disconnect_model_handlers':
fm-directory-view.c:9735:2: warning: pointer targets in passing argument 2 of 'disconnect_directory_handler' differ in signedness [-Wpointer-sign]
disconnect_directory_handler (view, &view->details->files_added_handler_id);
^
fm-directory-view.c:9718:1: note: expected 'int *' but argument is of type 'guint *'
disconnect_directory_handler (FMDirectoryView *view, int *id)
^
fm-directory-view.c:9736:2: warning: pointer targets in passing argument 2 of 'disconnect_directory_handler' differ in signedness [-Wpointer-sign]
disconnect_directory_handler (view, &view->details->files_changed_handler_id);
^
fm-directory-view.c:9718:1: note: expected 'int *' but argument is of type 'guint *'
disconnect_directory_handler (FMDirectoryView *view, int *id)
^
fm-directory-view.c:9737:2: warning: pointer targets in passing argument 2 of 'disconnect_directory_handler' differ in signedness [-Wpointer-sign]
disconnect_directory_handler (view, &view->details->done_loading_handler_id);
^
fm-directory-view.c:9718:1: note: expected 'int *' but argument is of type 'guint *'
disconnect_directory_handler (FMDirectoryView *view, int *id)
^
fm-directory-view.c:9738:2: warning: pointer targets in passing argument 2 of 'disconnect_directory_handler' differ in signedness [-Wpointer-sign]
disconnect_directory_handler (view, &view->details->load_error_handler_id);
^
fm-directory-view.c:9718:1: note: expected 'int *' but argument is of type 'guint *'
disconnect_directory_handler (FMDirectoryView *view, int *id)
^
fm-directory-view.c:9739:2: warning: pointer targets in passing argument 2 of 'disconnect_directory_as_file_handler' differ in signedness [-Wpointer-sign]
disconnect_directory_as_file_handler (view, &view->details->file_changed_handler_id);
^
fm-directory-view.c:9724:1: note: expected 'int *' but argument is of type 'guint *'
disconnect_directory_as_file_handler (FMDirectoryView *view, int *id)
^