pyfmt: Fix parameter with old bash version

Used to fail in bash 3.2 when called with --check

bin/pyfmt

@@ -19,13 +19,13 @@ cd "$(dirname "$0")/.."
 
 try bin/pyactivate -m black . "$@"
 
-args=("--fix")
+arg="--fix"
 
 while [[ $# -gt 0 ]]; do
   case $1 in
     --check)
       # ruff only supports --fix, not --check
-      args=()
+      arg=""
       shift
       ;;
     *)
@@ -35,6 +35,9 @@ while [[ $# -gt 0 ]]; do
   esac
 done
 
-try bin/pyactivate -m ruff "${args[@]}" --extend-exclude=misc/dbt-materialize .
-try bin/pyactivate -m ruff --target-version=py38 "${args[@]}" misc/dbt-materialize
+# We want empty arg to not do anything
+# shellcheck disable=SC2086
+try bin/pyactivate -m ruff $arg --extend-exclude=misc/dbt-materialize .
+# shellcheck disable=SC2086
+try bin/pyactivate -m ruff --target-version=py38 $arg misc/dbt-materialize
 try_status_report