Add php 8.1 support

Hello,

thanks for your plugin, i get 5 warnings running your plugin with Query Monitor.

Undefined array key "align"	
wp-content/plugins/ultimate-maps-by-supsystic/modules/maps/views/tpl/mapsMapStyles.php:19

Undefined array key "border_width"	
wp-content/plugins/ultimate-maps-by-supsystic/modules/maps/views/tpl/mapsMapStyles.php:20

Undefined array key "border_color"	
wp-content/plugins/ultimate-maps-by-supsystic/modules/maps/views/tpl/mapsMapStyles.php:20

Undefined array key "margin"	
wp-content/plugins/ultimate-maps-by-supsystic/modules/maps/views/tpl/mapsMapStyles.php:21

Undefined array key "classname"	
wp-content/plugins/ultimate-maps-by-supsystic/modules/maps/views/tpl/mapsDrawMap.php:4

Hope that helps