--delay=0 doesn't work for a running shutter instance had ran a delayed shot from command-line

Shutter version: 0.90 rev 1252

Steps to reproduce the problem, and what happend:
1. Have a running Shutter instance.
2. Invoke a delayed screenshot via command-line, such as 'shutter --delay=5 -a'
3. Invoke a --delay=0 screenshot via command-line, then a delayed shot will be taken using last --delay= parameter.

Invoking without --delay= switch produce the same problem. But having --delay= set to 0.0 performs a instant shot, and later shots will be using 0.0 as delay.

I hope --delay=0 could work as --delay=0.0 did, or a shot invoked without --delay= switch shouldn't be using last --delay= setting.