[xmonad] Segmentation fault when accidentally decorating a tabbed layout

[Weeble]

I'm using MultiToggle so that I can press WIN+D to toggle on window
decorations when I need to tell similar windows apart. However, I've
found that this causes a segmentation fault whenever I use it on a
tabbed layout. I assume this is because it's already decorated? I know
it may not make much sense to decorate it twice, but I don't think it
should segfault when I do this. I've tried to get updated versions
from darcs, but I don't really understand how all the dependencies
work, so I probably did something wrong.

I'm running Ubuntu and I believe I installed GHC using apt-get. I
can't remember how I originally installed Cabal, but I did "cabal
install X11" and so on to install the dependencies listed in the
readme. I synced up xmonad and XMonadContrib from darcs today and
rebuilt them and installed them using the "--user" option. The crashes
still happen. What should I do next?

In terms of experience my Haskell is pretty limited, and my knowledge
of package management in Haskell is next to zero. I know my way around
a command-line so I hope I'll be able to follow any instructions
without too much trouble, but I might need things spelled out for me,
particularly if it involves editing (or explaining!) my xmonad.hs
file.

My xmonad.hs file is attached.
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