update extension app

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1099 bbd45198-f89e-11dd-88c7-29a3b14d5316

components/module/extapp/extapp.c

@@ -28,7 +28,7 @@ int rt_application_entry(void)
 		else rt_kprintf("dlsym function5 failed.\n");
 	}
 
-	dlclose(handle);
+	if(handle != RT_NULL) dlclose(handle);
 
 	return 0;
 }