Make generate_exchange_uuid() always return the passed ast_str pointer.

I changed this code earlier to return NULL if it wasn't able to generate a UUID,
whereas the earlier code would always return the ast_str that was passed in.
Switch back to returning the ast_str, only set it to the empty string instead if
UUID generation fails.  We still do a validity check later which will catch this
and blow up if necessary.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@378000 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_calendar_exchange.c

@@ -246,7 +246,8 @@ static struct ast_str *generate_exchange_uuid(struct ast_str *uid)
 	struct ast_uuid *uuid = ast_uuid_generate();
 
 	if (!uuid) {
-		return NULL;
+		ast_str_set(&uid, 0, "%s", "");
+		return uid;
 	}
 
 	ast_str_set(&uid, 0, "%s", ast_uuid_to_str(uuid, buffer, AST_UUID_STR_LEN));