Not a game breaking issue, but quite annoying 
Upon installing 0.9 on my computer running Lubuntu 12.04, I proceeded to do a complete key remap. I went to ?->1 and removed the key assignments from all the actions. Then, starting from the top, I started to add my keybindings the way I like them. Once done, I rolled a new world and character and played as usual. When I ran Cataclysm the next day, I recieved this error message:
After pressing space the same message comes up again with the only difference being it says "“ull” instead of “null”. After pressing space a second time the game runs normally and my custom keybinds are still used, however, opening keymap.txt shows it’s contents as simply “NULL”, yet the file is 700+kB in size.
UPDATE::
I have managed to regen the keymap.txt file by opening Cataclysm, deleting the keymap.txt file, then going to ?->1 and remapping a key, thus making Cataclysm re-save the keymap.
EDIT:: I have also duplicated this post on GitHub.