Fallback on error in advice to ido-completing-read

If the ido-ubiquitous setup code in the ido-completing-read advice
encounters an error, the fallback completion method will be used
instead of ido completion.
Supress error in advice to ido-exit-minibuffer

If the old-style-default advice on ido-exit-minibuffer encounters an
error, the advice will be "skipped" and the function will be run
anyway.
Catch errors in ido-ubiquitous-with-override

The first argument to ido-ubiquitous-with-override is wrapped in a
call to "ignore-errors", so an error simply results in no override.
Fix indentation