This is a partial revert and rework of commit
c79575362e, for the `gsettings` script
only (the other completion scripts are fine).
I blindly added quoting to everything shellcheck told me to, without
testing it properly.
As it turns out, the `$schemadir` argument to `gsettings` invocations
was deliberately not quoted, so that it would expand to zero arguments
if unset, and two arguments (`--schemadir /some/path`) if set earlier in
the command-being-completed.
Quoting it meant that it expanded to one argument (the empty string) if
unset, which caused the `gsettings` subcommands to fail, and hence any
further tab completion to fail.
Fix that as suggested on https://www.shellcheck.net/wiki/SC2086 by
turning `schemadir` into an array, which either has zero members if
unset, or two members if set.
Signed-off-by: Philip Withnall <pwithnall@gnome.org>
70c0f3bff6