malloc/realloc success check

git-svn-id: https://hamlib.svn.sourceforge.net/svnroot/hamlib/trunk@2318 7ae35d74-ebe9-4afe-98af-79ac388436b8

src/mem.c

@@ -16,7 +16,7 @@
  *  Hamlib Interface - mem/channel calls
  *  Copyright (c) 2000-2006 by Stephane Fillod
  *
- *	$Id: mem.c,v 1.11 2006-10-15 00:27:51 aa6e Exp $
+ *	$Id: mem.c,v 1.12 2008-04-11 14:43:09 fillods Exp $
  *
  *   This library is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU Library General Public License as
@@ -215,6 +215,12 @@ static int generic_retr_extl(RIG *rig, const struct confparams *cfp, rig_ptr_t p
 				el_size+sizeof(struct ext_list));
 	}
 
+	if (!chan->ext_levels) {
+		rig_debug(RIG_DEBUG_ERR, "%s:%d memory allocation error!\n",
+				__FUNCTION__, __LINE__);
+		return -RIG_ENOMEM;
+	}
+
 	p->token = cfp->token;
 	rig_get_ext_level(rig, RIG_VFO_CURR, p->token, &p->val);
 	p++;