Update file InOperator.php

Closes #3453646

core/modules/views/src/Plugin/views/filter/InOperator.php

@@ -277,7 +277,7 @@ public function reduceValueOptions($input = NULL) {
         continue;
       }
       elseif (is_object($option) && !$option instanceof MarkupInterface) {
-        $keys = array_keys($option->option);
+        $keys = isset($option->option) && is_array($option->option) ? array_keys($option->option) : [];
         $key = array_shift($keys);
         if (isset($this->options['value'][$key])) {
           $options[$id] = $option;
@@ -337,7 +337,7 @@ public function adminSummary() {
     // Some filter_in_operator usage uses optgroups forms, so flatten it.
     $flat_options = OptGroup::flattenOptions($this->valueOptions);
 
-    if (!is_array($this->value)) {
+    if (!is_array($this->value) || $this->value === null) {
       return;
     }