Parse error in class-rwmb-group-field.php

I recently updated metabox group to 1.2.9 and the update threw a fatal error.

Parse error: syntax error, unexpected '[' in /home/lstudio/public_html/wp-content/plugins/meta-box-group/class-rwmb-group-field.php on line 284

I was able to fix this error by replacing the brackets in line 284 to an array.

Before:

                'attributes' => [
                    'data-current' => $field['default_state'],
                ],
        

After:

                'attributes' => array(
                    'data-current' => $field['default_state'],
                ),
        

This site is running php version 5.3.26. I did not see this error on my local install running php version 5.6.10. Is anything I might do in my theme files to guard against this error in future updates? I am also now working on upgrading the version of php.

I'm happy to provide any more information that you might find helpful.