Merge pull request #38 from pipedrive/quick-fix

Check if null quickfix

Author: Siim Kirjanen

src/APIHelper.php

@@ -64,9 +64,15 @@ public static function appendUrlWithQueryParameters(&$queryBuilder, $parameters)
         if (is_null($queryBuilder) || !is_string($queryBuilder)) {
             throw new InvalidArgumentException('Given value for parameter "queryBuilder" is invalid.');
         }
+
+        if (is_null($parameters)) {
+            return;
+        }
+
         $parameters = array_filter($parameters, function($value) {
             return isset($value);
         });
+
         if (empty($parameters)) {
             return;
         }