Fix compilation error when gluster::volume options are not set #183

Job	Run time
Puppet / Static validations	15s
Puppet / 8 (Ruby 3.2)	27s
Puppet / Puppet 8 - CentOS 7	1m 22s
Puppet / 7 (Ruby 2.7)	44s
Puppet / Puppet 7 - CentOS 7	1m 31s
Puppet / Distro Puppet - Archlinux rolling	1m 9s
Puppet / Puppet 8 - Ubuntu 20.04	2m 22s
Puppet / Puppet 7 - Ubuntu 20.04	1m 50s
Puppet / Puppet 8 - Ubuntu 22.04	1m 43s
Puppet / Puppet 7 - Ubuntu 22.04	1m 42s
Puppet / Test suite	1s
	13m 6s

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