Check if view argument is null before function call

Errors

Notice: Undefined index: in Drupal\advanced_search\AdvancedSearchQuery->alterView() 
(line 304 of /var/www/drupal/web/modules/contrib/advanced_search/src/AdvancedSearchQuery.php)

Error: Call to a member function getPlugin() on null in Drupal\advanced_search\AdvancedSearchQuery->alterView()
(line 304 of /var/www/drupal/web/modules/contrib/advanced_search/src/AdvancedSearchQuery.php)

To reproduce

Install FullCalendar Solr module
Create a view using the FullCalendar Solr view formatter
Enable Ajax
Go to the view and try to search using the Advanced Search block / facets

Islandora / advanced_search

Check if view argument is null before function call #30