Night Hacker is correct, the wingnami exception is because the variable isn't declared or set in 4.5 final. The problem is still present in the bugix release.
The issue was raised previously and
a hotfix provided by
CurtimusPrime92 (does what Night Hacker discussed, will work with non-modded games too).
If you're raising it with Oceanlab, the solution would be to declare the missing variable in Var.rpy, where most of the variables are declared. Ideally default should be used rather than define (define is intended for constants, default is intended for variables which change during gameplay).
default wingnami = False
As others have discussed, the issues has arisen due to the rewrite of the first half of Ch2. It worked fine as of 4.5 beta (before the rewrite). Previously wingnami was set during the shower scene early in Ch2, but it was doing so via the old method
$ wingnami = False
rather than using default to declare it properly.
When Ocean rewrote the shower scene he removed the sections which set wingnami, but didn't remove the subsequent if statements which employ it, resulting in the exception when it tries to address a variable which no longer exists.
I believe this oversight is partly because someone else was previously doing the coding, so Ocean is still coming to grips with the code to some extent.