Don't crash if the 'o' option of ControlPlayback is used without any value.

(closes issue #11375)
Reported by: johan


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@89570 65c4cc65-6c06-0410-ace0-fbb531ad65f3

apps/app_controlplayback.c

@@ -124,7 +124,7 @@ static int controlplayback_exec(struct ast_channel *chan, void *data)
 
 	if (args.options) {
 		ast_app_parse_options(cpb_opts, &opts, opt_args, args.options);		
-		if (ast_test_flag(&opts, OPT_OFFSET))
+		if (ast_test_flag(&opts, OPT_OFFSET) && !ast_strlen_zero(opt_args[OPT_ARG_OFFSET]))
 			offsetms = atol(opt_args[OPT_ARG_OFFSET]);
 	}