Do not disable keyboard entirely in case compose table fail to load

[showier-drastic]

Under my buildroot environment, for some reason I get "Could not create compose table from locale." message, which entirely disables keyboard. As I am using a custom keyboard design without any need for compose keys (and I am sure many others are), let's make compose table a non-critical dependency, and allow using keyboard without it.

xkbcommon: ERROR: couldn't find a Compose file for locale "C" (mapped to "C")
keyboard.c: Could not create compose table from locale.
keyboard.c: Compose table not available. Compose key sequences will be disabled.