Superputty not respecting "Forbid resizing completely" option when session is first opened.

[techni-ca]

Describe the bug
When opening a session, SuperPuTTY resizes it to fill the tab, even if the session explicitly forbids resizing.

To Reproduce
Steps to reproduce the behavior:

1. In PuTTY, save a session with "Forbid resizing completely" checked in the "Window" menu.
   (Make it a smallish font and a smaller width & height than you would normally use in SuperPuTTY).
2. Make a new session in SuperPuTTY that uses that PuTTY session profile.
3. Open the session with the SuperPuTTY window nice and large. It will resize the font to fit the SuperPuTTY window (the behavior that you would expect if "Change the size of the font" had been checked in PuTTY).

Expected behavior
Right click on the tab for the open session from step 3, above, and click "Change Settings". Then click "Apply" in the PuTTY settings menu that appears. The session will resize to the the font, width & height originally set for the session. That's how it should open initially.