Minor bug in single instance feature

Hey,

This bug happens when "Single Instance" and "Minimize To tray" features are enabled.

When SmartFTP is minimized to tray, and then you try to open another instance, the previous SmartFTP window will appear, but the icon will still be in the tray. (this isn't the same behaviour as the regular maximizing, which removes the smartftp tray icon).

This is a small bug, but still it could confuse you into thinking that you have an extra copy of SmartFTP running.