gtk_tree_model_filter_row_deleted: don't emit signals too early
gtk_tree_model_filter_row_deleted was emitting ::row-deleted while the internal state of the model was still in disarray, causing segfaults e.g. when mapping the file chooser with accessibility turned on. This is just a bandaid fix, and doesn't try address any of the deeper problems of the filter model code. I did take the time to reduce rampant variable shadowing in that function, though.