Update ViewsJsonFilter.php

Added a check to make sure the value is an array, as well as non-empty.

src/Plugin/views/filter/ViewsJsonFilter.php

@@ -232,7 +232,11 @@ class ViewsJsonFilter extends FilterPluginBase {
   public function generate() {
     $operator = $this->options['operator'];
     $key = $this->options['key'];
-    $value = !empty($this->value) && $this->isExposed() ? reset($this->value) : $this->options['value'];
+    if(is_array($this->value) && !empty($this->value)) {
+      $value = reset($this->value);
+    } else {
+      $value = $this->options['value'];
+    }
 
     return [$key, $operator, $value];
   }