fix: handle empty arrays with set -u in pattern.sh (#91)

On macOS with podman machine, PKI_HOST_MOUNT_ARGS and EXTRA_ARGS_ARRAY
can be empty arrays. When using set -u (nounset), bash throws
"unbound variable" errors when expanding empty arrays with [@].

Use conditional expansion "${array[@]+"${array[@]}"}" which expands
to nothing if the array is empty, avoiding the unbound variable error.

This fixes: ./pattern.sh: line 93: PKI_HOST_MOUNT_ARGS[@]: unbound variable

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: butler54

pattern.sh

@@ -114,12 +114,12 @@ podman run -it --rm --pull=newer \
     -e TOKEN_SECRET \
     -e UUID_FILE \
     -e VALUES_SECRET \
-    "${PKI_HOST_MOUNT_ARGS[@]}" \
+    "${PKI_HOST_MOUNT_ARGS[@]+"${PKI_HOST_MOUNT_ARGS[@]}"}" \
     -v "$(pwd -P)":"$(pwd -P)" \
     -v "${HOME}":"${HOME}" \
     -v "${HOME}":/pattern-home \
     "${PODMAN_ARGS[@]}" \
-    "${EXTRA_ARGS_ARRAY[@]}" \
+    "${EXTRA_ARGS_ARRAY[@]+"${EXTRA_ARGS_ARRAY[@]}"}" \
     -w "$(pwd -P)" \
     "$PATTERN_UTILITY_CONTAINER" \
     "$@"