default param fix for dart

Author: lohanidamodar

templates/dart/lib/client.dart.twig

@@ -68,6 +68,12 @@ class Client {
             };
         }
 
+        params.keys.forEach((key) {
+          if (params[key] == null) {
+            params.remove(key);
+          }
+        });
+
         // Origin is hardcoded for testing
         Options options = Options(
             headers: {...this.headers!, ...headers},

templates/dart/lib/services/service.dart.twig

@@ -2,7 +2,7 @@ part of {{ language.params.packageName }};
 
 {% macro parameter(parameter) %}
 {% if parameter.name == 'orderType' %}{% if parameter.required %}required {% endif %}{{ 'OrderType orderType = OrderType.asc' }}{% else %}
-{% if parameter.required %}required {% endif %}{{ parameter.type | typeName }} {{ parameter.name | caseCamel }}{{ parameter | paramDefault | escapeDollarSign }}{% endif %}
+{% if parameter.required %}required {{ parameter.type | typeName }}{% else %}{{ parameter.type | typeName }}?{% endif %} {{ parameter.name | caseCamel }}{% if parameter.required %}{{ parameter | paramDefault | escapeDollarSign }}{% endif %}{% endif %}
 {% endmacro %}
 {% macro method_parameters(parameters) %}
 {% if parameters.all|length > 0 %}{{ '{' }}{% for parameter in parameters.all %}{{ _self.parameter(parameter) }}{% if not loop.last %}, {% endif %}{% endfor %}{{ '}' }}{% endif %}