--- DO NOT USE -- In this example, buffer == NULL WHY?

gistfile1.c

/*
 * transformadd.h
 * 
 * Copyright 2012 moebiuseye <moebiuseye@deadlyweapon>
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA 02110-1301, USA.
 */

#include <geanyplugin.h>
#include <assert.h>

GeanyPlugin  	*geany_plugin;
GeanyData		*geany_data;
GeanyFunctions	*geany_functions;

/* _c_ means current */
static gint _c_tab; 

void print_hello( GtkWidget *w, gpointer data) {
	GtkWidget *notebook = geany->main_widgets->notebook;
	_c_tab = gtk_notebook_get_current_page( GTK_NOTEBOOK(notebook) );
	GtkTextView *current_tab = GTK_TEXT_VIEW(
		gtk_notebook_get_nth_page( GTK_NOTEBOOK(notebook), _c_tab) );
	
	if ( current_tab == NULL ) {
		dialogs_show_msgbox( GTK_MESSAGE_INFO, "current_tab==NULL" ); return;
	}
	
	GtkTextBuffer *buffer = gtk_text_view_get_buffer( current_tab );
	
	if (  buffer == NULL ) {
		dialogs_show_msgbox( GTK_MESSAGE_INFO, "buffer==NULL" ); return;
	}
	
	GtkTextIter *start = NULL , *end = NULL;
	gtk_text_buffer_get_start_iter( buffer, start );
	gtk_text_buffer_get_end_iter(   buffer, end );
	int b = 1;
	char *text = (char*)gtk_text_buffer_get_text ( buffer, 
		start , end, (gboolean)b );
	
	if (  text == NULL ) {
		dialogs_show_msgbox( GTK_MESSAGE_INFO, "text==NULL" ); return;
	}
	
	dialogs_show_msgbox( GTK_MESSAGE_INFO, text );
}