fix stripos error on contains filter

Closes #3462164

Accessing the string value of the array in the match for 'contains' to resolve the error

src/Plugin/views/filter/ViewsCsvFilter.php

@@ -226,6 +226,9 @@ class ViewsCsvFilter extends FilterPluginBase {
     $selected_column = $this->options['key'];
     $info = $this->operators();
     if (!empty($info[$this->operator]['method'])) {
+      if (is_array($this->value)) {
+        $this->value = $this->value[0];
+      }
       $this->{$info[$this->operator]['method']}($selected_column);
     }
   }